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KSH(1)									KSH(1)

NAME
       ksh,  rksh,  pfksh  - KornShell, a standard/restricted command and pro‐
       gramming language

NOTE
       Currently, rksh and pfksh are not available on Mac OS X / Darwin.

SYNOPSIS
       ksh [ ±abcefhikmnoprstuvxBCDP ] [ -R file ] [ ±o option ] ... [ -  ]  [
       arg ... ]
       rksh  [ ±abcefhikmnoprstuvxBCD ] [ -R file ] [ ±o option ] ...  [ - ] [
       arg ... ]

DESCRIPTION
       Ksh is a command and programming language that executes	commands  read
       from a terminal or a file.  Rksh is a restricted version of the command
       interpreter ksh; it is used to set up login names and  execution	 envi‐
       ronments whose capabilities are more controlled than those of the stan‐
       dard shell.  Rpfksh is a profile shell version of  the  command	inter‐
       preter ksh; it is used to to execute commands with the attributes spec‐
       ified by the user's profiles (see pfexec(1)).  See Invocation below for
       the meaning of arguments to the shell.

   Definitions.
       A metacharacter is one of the following characters:

	      ;	  &   (	  )   ⎪	  <   >	  new-line   space   tab

       A  blank	 is a tab or a space.  An identifier is a sequence of letters,
       digits, or underscores starting with a letter or	 underscore.   Identi‐
       fiers  are used as components of variable names.	 A vname is a sequence
       of one or more identifiers separated by a . and optionally preceded  by
       a  ..   Vnames  are  used  as function and variable names.  A word is a
       sequence of characters from the character set defined  by  the  current
       locale, excluding non-quoted metacharacters.

       A  command  is a sequence of characters in the syntax of the shell lan‐
       guage.  The shell reads each command and carries out the desired action
       either  directly or by invoking separate utilities.  A built-in command
       is a command that is carried out by the shell itself without creating a
       separate	 process.   Some  commands are built-in purely for convenience
       and are not documented here.  Built-ins that cause side effects in  the
       shell environment and built-ins that are found before performing a path
       search (see Execution below) are documented here.  For historical  rea‐
       sons,  some  of these built-ins behave differently than other built-ins
       and are called special built-ins.

   Commands.
       A simple-command is  a  list  of	 variable  assignments	(see  Variable
       Assignments  below) or a sequence of blank separated words which may be
       preceded by a list of variable  assignments  (see  Environment  below).
       The  first  word	 specifies  the	 name  of  the command to be executed.
       Except as specified below, the remaining words are passed as  arguments
       to  the invoked command.	 The command name is passed as argument 0 (see
       exec(2)).  The value of a simple-command is its exit status;  0-255  if
       it  terminates  normally;  256+signum  if it terminates abnormally (the
       name of the signal corresponding to the exit status can be obtained via
       the -l option of the kill built-in utility).

       A  pipeline  is a sequence of one or more commands separated by ⎪.  The
       standard output of each command but the last is connected by a  pipe(2)
       to the standard input of the next command.  Each command, except possi‐
       bly the last, is run as a separate process; the	shell  waits  for  the
       last  command  to terminate.  The exit status of a pipeline is the exit
       status of the last command unless the pipefail option is enabled.  Each
       pipeline	 can be preceded by the reserved word !	 which causes the exit
       status of the pipeline to become 0 if the exit status of the last  com‐
       mand is non-zero, and 1 if the exit status of the last command is 0.

       A  list	is  a sequence of one or more pipelines separated by ;, &, ⎪&,
       &&, or ⎪⎪, and optionally terminated by ;, &, or	 ⎪&.   Of  these  five
       symbols,	 ;,  &, and ⎪& have equal precedence, which is lower than that
       of && and ⎪⎪.  The symbols && and ⎪⎪ also  have	equal  precedence.   A
       semicolon (;) causes sequential execution of the preceding pipeline; an
       ampersand (&) causes asynchronous execution of the  preceding  pipeline
       (i.e.,  the shell does not wait for that pipeline to finish).  The sym‐
       bol ⎪& causes asynchronous execution of the preceding pipeline  with  a
       two-way	pipe  established  to the parent shell; the standard input and
       output of the spawned pipeline can be written to and read from  by  the
       parent shell by applying the redirection operators <& and >& with arg p
       to commands and by using -p option of the built-in  commands  read  and
       print described later.  The symbol && (⎪⎪) causes the list following it
       to be executed only if the preceding pipeline returns a zero (non-zero)
       value.	One  or more new-lines may appear in a list instead of a semi‐
       colon, to delimit a command.  The first item  of the first pipeline  of
       a  list	that is a simple command not beginning with a redirection, and
       not occurring within a while, until, or if list, can be preceded	 by  a
       semicolon.   This  semicolon  is	 ignored  unless  the showme option is
       enabled as described with the set built-in below.

       A command is either a simple-command or one of the  following.	Unless
       otherwise  stated,  the value returned by a command is that of the last
       simple-command executed in the command.

       for vname [ in word ... ] ;do list ;done
	      Each time a for command is executed, vname is set	 to  the  next
	      word  taken  from the in word list.  If in word ...  is omitted,
	      then the for command executes the do list once  for  each	 posi‐
	      tional  parameter	 that  is  set	starting from 1 (see Parameter
	      Expansion below).	 Execution ends when there are no  more	 words
	      in the list.

       for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
	      The  arithmetic  expression expr1 is evaluated first (see Arith‐
	      metic evaluation below).	The  arithmetic	 expression  expr2  is
	      repeatedly  evaluated  until  it evaluates to zero and when non-
	      zero, list is executed and the arithmetic expression expr3 eval‐
	      uated.   If  any expression is omitted, then it behaves as if it
	      evaluated to 1.

       select vname [ in word ... ] ;do list ;done
	      A select command prints on standard error	 (file	descriptor  2)
	      the set of words, each preceded by a number.  If in word ...  is
	      omitted, then the positional parameters starting from 1 are used
	      instead  (see  Parameter	Expansion  below).   The PS3 prompt is
	      printed and a line is read from the  standard  input.   If  this
	      line consists of the number of one of the listed words, then the
	      value of the variable vname is set to the word corresponding  to
	      this  number.   If  this	line  is  empty, the selection list is
	      printed again.  Otherwise the value of the variable vname is set
	      to  null.	  The contents of the line read from standard input is
	      saved in the variable REPLY.  The	 list  is  executed  for  each
	      selection	 until	a break or end-of-file is encountered.	If the
	      REPLY variable is set to null by the execution of list, then the
	      selection	 list  is printed before displaying the PS3 prompt for
	      the next selection.

       case word in [ [(]pattern [ ⎪ pattern ] ... ) list ;; ] ... esac
	      A case command executes the list associated with the first  pat‐
	      tern that matches word.  The form of the patterns is the same as
	      that used for file-name generation  (see	File  Name  Generation
	      below).	The ;; operator causes execution of case to terminate.
	      If ;& is used in place of ;; the next subsequent list,  if  any,
	      is executed.

       if list ;then list [ ;elif list ;then list ] ... [ ;else list ] ;fi
	      The list following if is executed and, if it returns a zero exit
	      status, the list following the first then is  executed.	Other‐
	      wise,  the  list following elif is executed and, if its value is
	      zero, the list following the next	 then  is  executed.   Failing
	      each successive elif list, the else list is executed.  If the if
	      list has non-zero exit status and there is no  else  list,  then
	      the if command returns a zero exit status.

       while list ;do list ;done
       until list ;do list ;done
	      A	 while	command repeatedly executes the while list and, if the
	      exit status of the last command in the list  is  zero,  executes
	      the  do  list; otherwise the loop terminates.  If no commands in
	      the do list are executed, then the while command returns a  zero
	      exit  status;  until may be used in place of while to negate the
	      loop termination test.

       ((expression))
	      The expression is evaluated using the rules for arithmetic eval‐
	      uation  described below.	If the value of the arithmetic expres‐
	      sion is non-zero, the exit status is 0, otherwise the exit  sta‐
	      tus is 1.

       (list)
	      Execute list in a separate environment.  Note, that if two adja‐
	      cent open parentheses are needed for nesting, a  space  must  be
	      inserted	to  avoid  evaluation  as  an  arithmetic  command  as
	      described above.

       { list;}
	      list is simply executed.	Note that unlike the metacharacters  (
	      and  ),  { and } are reserved words and must occur at the begin‐
	      ning of a line or after a ; in order to be recognized.

       [[ expression ]]
	      Evaluates expression and returns a zero exit status when expres‐
	      sion is true.  See Conditional Expressions below, for a descrip‐
	      tion of expression.

       function varname { list ;}
       varname () { list ;}
	      Define a function which is referenced by	varname.   A  function
	      whose  varname contains a .  is called a discipline function and
	      the portion of the varname preceding the last .  must  refer  to
	      an  existing  variable.  The body of the function is the list of
	      commands between { and }.	 A function defined with the  function
	      varname syntax can also be used as an argument to the .  special
	      built-in command to get the equivalent behavior as if  the  var‐
	      name() syntax were used to define it.  (See Functions below.)

       namespace identifier { list ;}
	      Defines or uses the name space identifier^ and runs the commands
	      in list^ in this name space.  (See Name Spaces below.)

       & [ name [ arg... ]  ]
	      Causes subsequent list commands terminated by & to be placed  in
	      the  background  job  pool  name.	  If name is omitted a default
	      unnamed pool is used.  Commands in a named background  pool  may
	      be executed remotely.

       time [ pipeline ]
	      If  pipeline is omitted the user and system time for the current
	      shell and completed  child  processes  is	 printed  on  standard
	      error.   Otherwise, pipeline is executed and the elapsed time as
	      well as the user and system time are printed on standard	error.
	      The TIMEFORMAT variable may be set to a format string that spec‐
	      ifies how the timing information should be displayed.  See Shell
	      Variables below for a description of the TIMEFORMAT variable.

       The  following reserved words are recognized as reserved only when they
       are the first word of a command and are not quoted:

       if then else elif fi case esac for while until do  done	{  }  function
       select time [[ ]] !

   Variable Assignments.
       One  or	more variable assignments can start a simple command or can be
       arguments to the typeset, enum, export, or  readonly  special  built-in
       commands	 as  well  as  to other declaration commands created as types.
       The syntax for an assignment is of the form:

       varname=word
       varname[word]=word
	      No space is permitted between varname and the = or between = and
	      word.

       varname=(assign_list)
	      No space is permitted between varname and the =.	An assign_list
	      can be one of the following:
		      word ...
			     Indexed array assignment.
		      [word]=word ...
			     Associative array	assignment.   If  preceded  by
			     typeset  -a  this	will  create  an indexed array
			     instead.
		      assignment ...
			     Compound variable	assignment.   This  creates  a
			     compound  variable	 varname with sub-variables of
			     the form varname.name, where  name	 is  the  name
			     portion of assignment.  The value of varname will
			     contain all the assignment elements.   Additional
			     assignments made to sub-variables of varname will
			     also be displayed as part of the  value  of  var‐
			     name.   If	 no assignments are specified, varname
			     will be a compound variable allowing  subsequence
			     child elements to be defined.
		      typeset [options] assignment ...
			     Nested variable assignment.  Multiple assignments
			     can be specified by separating each of them  with
			     a	;.   The  previous  value  is unset before the
			     assignment.  Other declaration commands  such  as
			     readonly,	enum,  and  other declaration commands
			     can be used in place of typeset.
		      . filename
			     Include  the  assignment  commands	 contained  in
			     filename.

       In addition, a += can be used in place of the = to signify adding to or
       appending to the previous value.	 When += is applied to	an  arithmetic
       type,  word  is	evaluated as an arithmetic expression and added to the
       current value.  When applied to a string variable, the value defined by
       word  is appended to the value.	For compound assignments, the previous
       value is not unset and the new values are appended to the current  ones
       provided that the types are compatible.

       The  right  hand side of a variable assignment undergoes all the expan‐
       sion listed below except word splitting, brace expansion, and file name
       generation.   When  the	left  hand side is an assignment is a compound
       variable and the right hand is the name of  a  compound	variable,  the
       compound	 variable  on the right will be copied or appended to the com‐
       pound variable on the left.

   Comments.
       A word beginning with # causes that word and all the following  charac‐
       ters up to a new-line to be ignored.
   Aliasing.
       The  first  word of each command is replaced by the text of an alias if
       an alias for this word has been defined.	 An alias name consists of any
       number of characters excluding metacharacters, quoting characters, file
       expansion characters,  parameter	 expansion  and	 command  substitution
       characters,  and =.  The replacement string can contain any valid shell
       script including the metacharacters listed above.  The  first  word  of
       each  command  in  the  replaced	 text,	other than any that are in the
       process of being replaced, will be tested for  aliases.	 If  the  last
       character  of  the  alias  value is a blank then the word following the
       alias will also be checked for alias substitution.  Aliases can be used
       to  redefine  built-in  commands	 but  cannot  be  used to redefine the
       reserved words listed above.  Aliases can be created  and  listed  with
       the alias command and can be removed with the unalias command.
       Aliasing	 is  performed	when scripts are read, not while they are exe‐
       cuted.  Therefore, for an alias to take effect,	the  alias  definition
       command	has  to	 be  executed  before the command which references the
       alias is read.
       The following aliases are compiled into the shell but can be  unset  or
       redefined:
			   autoload=′typeset -fu′
			   command=′command  ′
			   compound=′typeset -C′
			   fc=hist
			   float=′typeset -lE′
			   functions=′typeset -f′
			   hash=′alias -t --′
			   history=′hist -l′
			   integer=′typeset -li′
			   nameref=′typeset -n′
			   nohup=′nohup	 ′
			   r=′hist -s′
			   redirect=′command exec′
			   source=′command .′
			   stop=′kill -s STOP′
			   suspend=′kill -s STOP $$′
			   times=′{ { time;} 2>&1;}′
			   type=′whence -v′

   Tilde Substitution.
       After  alias  substitution is performed, each word is checked to see if
       it begins with an unquoted ∼.  For tilde substitution, word also refers
       to  the	word  portion  of parameter expansion (see Parameter Expansion
       below).	If it does, then the word up to a / is checked to  see	if  it
       matches	a user name in the password database (See getpwname(3).)  If a
       match is found, the ∼ and the matched login name are  replaced  by  the
       login  directory of the matched user.  If no match is found, the origi‐
       nal text is left unchanged.  A ∼ by itself, or in  front	 of  a	/,  is
       replaced	 by  $HOME.  A ∼ followed by a + or - is replaced by the value
       of $PWD and $OLDPWD respectively.

       In addition, when expanding a variable assignment,  tilde  substitution
       is attempted when the value of the assignment begins with a ∼, and when
       a ∼ appears after a :.  The : also terminates a ∼ login name.

   Command Substitution.
       The standard output from a command list enclosed	 in  parentheses  pre‐
       ceded  by  a dollar sign ( $(list) ), or in a brace group preceded by a
       dollar sign ( ${ list;} ), or in a pair of grave accents	 (``)  may  be
       used  as part or all of a word; trailing new-lines are removed.	In the
       second case, the { and } are treated as a reserved words so that { must
       be  followed  by a blank and } must appear at the beginning of the line
       or follow a ;.  In the third (obsolete) form, the  string  between  the
       quotes  is  processed for special quoting characters before the command
       is executed (see Quoting below).	 The command substitution $(cat	 file)
       can  be	replaced  by  the equivalent but faster $(<file).  The command
       substitution $(n<#) will expand to the current  byte  offset  for  file
       descriptor n.  Except for the second form, the command list is run in a
       subshell so that no side effects are possible.  For  the	 second	 form,
       the final } will be recognized as a reserved word after any token.

   Arithmetic Substitution.
       An  arithmetic  expression enclosed in double parentheses preceded by a
       dollar sign ( $(()) ) is	 replaced  by  the  value  of  the  arithmetic
       expression within the double parentheses.

   Process Substitution.
       This feature is only available on versions of the UNIX operating system
       that support the /dev/fd directory for naming open files.  Each command
       argument	 of  the  form	<(list) or >(list) will run process list asyn‐
       chronously connected to some file in /dev/fd.  The name	of  this  file
       will  become  the  argument  to	the  command.	If  the form with > is
       selected then writing on this file will provide input for list.	 If  <
       is used, then the file passed as an argument will contain the output of
       the list process.  For example,

	      paste <(cut -f1  file1)  <(cut  -f3  file2)  |  tee  >(process1)
	      >(process2)

       cuts fields 1 and 3 from the files file1 and file2 respectively, pastes
       the results together, and  sends	 it  to	 the  processes	 process1  and
       process2,  as  well  as putting it onto the standard output.  Note that
       the file, which is passed as an argument to  the	 command,  is  a  UNIX
       pipe(2) so programs that expect to lseek(2) on the file will not work.

       Process	substitution  of  the form <(list) can also be used with the <
       redirection operator which causes the output of	list  to  be  standard
       input or the input for whatever file descriptor is specified.

   Parameter Expansion.
       A parameter is a variable, one or more digits, or any of the characters
       ∗, @, #, ?, -, $, and !.	 A variable is denoted by a vname.  To	create
       a variable whose vname contains a ., a variable whose vname consists of
       everything before the last . must already  exist.   A  variable	has  a
       value  and  zero	 or more attributes.  Variables can be assigned values
       and attributes by using the  typeset  special  built-in	command.   The
       attributes  supported by the shell are described later with the typeset
       special	built-in  command.   Exported  variables   pass	  values   and
       attributes to the environment.

       The  shell supports both indexed and associative arrays.	 An element of
       an array variable is referenced by a subscript.	 A  subscript  for  an
       indexed	array  is  denoted by an arithmetic expression (see Arithmetic
       evaluation below) between a [ and a ].  To assign values to an  indexed
       array, use vname=(value ...) or set -A vname  value ... .  The value of
       all  non-negative  subscripts  must  be	in  the	 range	of  0  through
       4,194,303.  A negative subscript is treated as an offset from the maxi‐
       mum current index +1 so that -1 refers to the  last  element.   Indexed
       arrays  can  be declared with the -a option to typeset.	Indexed arrays
       need not be declared.  Any reference to a variable with	a  valid  sub‐
       script is legal and an array will be created if necessary.

       An  associative array is created with the -A option to typeset.	A sub‐
       script for an associative array is denoted by a string enclosed between
       [ and ].

       Referencing  any array without a subscript is equivalent to referencing
       the array with subscript 0.

       The value of a variable may be assigned by writing:

	      vname=value [ vname=value ] ...

       or
	      vname[subscript]=value [ vname[subscript]=value ] ...
       Note that no space is allowed before or after the =.
       A nameref is a variable that is a reference  to	another	 variable.   A
       nameref	is created with the -n attribute of typeset.  The value of the
       variable at the time of the typeset command becomes the	variable  that
       will  be referenced whenever the nameref variable is used.  The name of
       a nameref cannot contain a ..  When a variable or  function  name  con‐
       tains  a	 .,  and the portion of the name up to the first . matches the
       name of a nameref, the variable referred to is  obtained	 by  replacing
       the  nameref  portion  with  the name of the variable referenced by the
       nameref.	 If a nameref is used as the index of a for loop, a name  ref‐
       erence  is established for each item in the list.  A nameref provides a
       convenient way to refer to the variable inside a function whose name is
       passed  as  an  argument	 to a function.	 For example, if the name of a
       variable is passed as the first argument to a function, the command
	      typeset -n var=$1
       inside the function causes references and assignments to var to be ref‐
       erences	and  assignments to the variable whose name has been passed to
       the function.
       If any of the floating point attributes, -E, -F, or -X, or the  integer
       attribute,  -i,	is  set for vname, then the value is subject to arith‐
       metic evaluation as described below.
       Positional parameters, parameters denoted by a number, may be  assigned
       values with the set special built-in command.  Parameter $0 is set from
       argument zero when the shell is invoked.
       The character $ is used to introduce substitutable parameters.
       ${parameter}
	      The shell reads all the characters from ${ to the matching }  as
	      part  of the same word even if it contains braces or metacharac‐
	      ters.  The value, if any, of the parameter is substituted.   The
	      braces  are  required  when  parameter  is followed by a letter,
	      digit, or underscore that is not to be interpreted  as  part  of
	      its  name,  when the variable name contains a ..	The braces are
	      also required when a variable is subscripted unless it  is  part
	      of  an  Arithmetic  Expression  or a Conditional Expression.  If
	      parameter is one or more digits then it is a positional  parame‐
	      ter.   A	positional  parameter  of  more than one digit must be
	      enclosed in braces.  If parameter is ∗ or @, then all the	 posi‐
	      tional  parameters, starting with $1, are substituted (separated
	      by a field separator character).	If an array  vname  with  sub‐
	      script  ∗	 @,  or	 of the form sub1 ..  sub2.  is used, then the
	      value for each of the elements between sub1 and  sub2  inclusive
	      (or  all	elements for ∗ and @) is substituted, separated by the
	      first character of the value of IFS.
       ${#parameter}
	      If parameter is ∗ or @, the number of positional	parameters  is
	      substituted.   Otherwise, the length of the value of the parame‐
	      ter is substituted.
       ${#vname[*]}
       ${#vname[@]}
	      The number of elements in the array vname is substituted.

       ${@vname}
	      Expands to  the  type  name  (See	 Type  Variables    below)  or
	      attributes of the variable referred to by vname.
       ${!vname}
	      Expands  to the name of the variable referred to by vname.  This
	      will be vname except when vname is a name reference.
       ${!vname[subscript]}
	      Expands to name of the subscript unless subscript is *,  @.   or
	      of  the  form  sub1  ..  sub2.  When subscript is *, the list of
	      array subscripts for vname is generated.	For a variable that is
	      not  an array, the value is 0 if the variable is set.  Otherwise
	      it is null.  When subscript is @, same  as  above,  except  that
	      when  used in double quotes, each array subscript yields a sepa‐
	      rate argument.  When subscript is of the form sub1 ..   sub2  it
	      expands  to  the list of subscripts between sub1 and sub2 inclu‐
	      sive using the same quoting rules as @.
       ${!prefix*}
	      Expands to the names of the variables  whose  names  begin  with
	      prefix.
       ${parameter:-word}
	      If  parameter  is set and is non-null then substitute its value;
	      otherwise substitute word.
       ${parameter:=word}
	      If parameter is not set or is null then  set  it	to  word;  the
	      value  of the parameter is then substituted.  Positional parame‐
	      ters may not be assigned to in this way.
       ${parameter:?word}
	      If parameter is set and is non-null then substitute  its	value;
	      otherwise,  print	 word and exit from the shell (if not interac‐
	      tive).  If word is omitted then a standard message is printed.
       ${parameter:+word}
	      If parameter is set and is non-null then substitute word; other‐
	      wise substitute nothing.
       In the above, word is not evaluated unless it is to be used as the sub‐
       stituted string, so that, in the following  example,  pwd  is  executed
       only if d is not set or is null:
	      print ${d:-$(pwd)}
       If  the	colon  (  :  ) is omitted from the above expressions, then the
       shell only checks whether parameter is set or not.
       ${parameter:offset:length}
       ${parameter:offset}
	      Expands to the portion of the value of parameter starting at the
	      character (counting from 0) determined by expanding offset as an
	      arithmetic expression and consisting of the number of characters
	      determined  by  the arithmetic expression defined by length.  In
	      the second form, the remainder of the value is used.  If A nega‐
	      tive  offset  counts  backwards from the end of parameter.  Note
	      that one or more blanks is required in front of a minus sign  to
	      prevent  the  shell  from	 interpreting  the operator as :-.  If
	      parameter is ∗ or @, or is an array name indexed by ∗ or @, then
	      offset  and  length  refer to the array index and number of ele‐
	      ments respectively.  A negative offset is taken relative to  one
	      greater  than  the  highest  subscript  for indexed arrays.  The
	      order for associate arrays is unspecified.
       ${parameter#pattern}
       ${parameter##pattern}
	      If the shell pattern matches  the	 beginning  of	the  value  of
	      parameter,  then the value of this expansion is the value of the
	      parameter with the matched portion deleted; otherwise the	 value
	      of  this parameter is substituted.  In the first form the small‐
	      est matching pattern is deleted  and  in	the  second  form  the
	      largest matching pattern is deleted.  When parameter is @, *, or
	      an array variable with subscript @ or *, the substring operation
	      is applied to each element in turn.

       ${parameter%pattern}
       ${parameter%%pattern}
	      If  the shell pattern matches the end of the value of parameter,
	      then the value of this expansion is the value of	the  parameter
	      with the matched part deleted; otherwise substitute the value of
	      parameter.  In the first form the smallest matching  pattern  is
	      deleted  and  in the second form the largest matching pattern is
	      deleted.	When parameter is @, *, or an array variable with sub‐
	      script  @	 or *, the substring operation is applied to each ele‐
	      ment in turn.

       ${parameter/pattern/string}
       ${parameter//pattern/string}
       ${parameter/#pattern/string}
       ${parameter/%pattern/string}
	      Expands parameter and replaces the longest match of pattern with
	      the  given  string.  Each occurrence of \n in string is replaced
	      by the portion of parameter that matches the  n-th  sub-pattern.
	      In  the  first  form,  only  the	first occurrence of pattern is
	      replaced.	 In  the  second  form,	 each  match  for  pattern  is
	      replaced by the given string.  The third form restricts the pat‐
	      tern match to the beginning of the string while the fourth  form
	      restricts	 the  pattern  match  to  the end of the string.  When
	      string is null, the pattern will be deleted and the /  in	 front
	      of  string  may be omitted.  When parameter is @, *, or an array
	      variable with subscript @ or *, the  substitution	 operation  is
	      applied  to each element in turn.	 In this case, the string por‐
	      tion of word will be re-evaluated for each element.

       The following parameters are automatically set by the shell:
	      #	     The number of positional parameters in decimal.
	      -	     Options supplied to the shell on invocation or by the set
		     command.
	      ?	     The decimal value returned by the last executed command.
	      $	     The process number of this shell.
	      _	     Initially,	 the value of _ is an absolute pathname of the
		     shell or script being executed as passed in the  environ‐
		     ment.   Subsequently  it is assigned the last argument of
		     the previous command.  This parameter is not set for com‐
		     mands  which  are	asynchronous.	This parameter is also
		     used to hold the name of  the  matching  MAIL  file  when
		     checking for mail.	 While defining a compound variable or
		     a type, _ is initialized as a reference to	 the  compound
		     variable or type.	When a discipline function is invoked,
		     _ is initialized as a reference to the  variable  associ‐
		     ated  with	 the call to this function.  Finally when _ is
		     used as the name of the first variable of a type  defini‐
		     tion,  the new type is derived from the type of the first
		     variable (See Type Variables  below.).
	      !	     The process id or the pool name and  job  number  of  the
		     last  background  command	invoked or the most recent job
		     put in the	 background  with  the	bg  built-in  command.
		     Background	 jobs  started	in a named pool will be in the
		     form pool.number where pool is the pool name  and	number
		     is the job number within that pool.
	      .sh.command
		     When  processing a DEBUG trap, this variable contains the
		     current command line that is about to run.
	      .sh.edchar
		     This variable contains the value of the keyboard  charac‐
		     ter  (or sequence of characters if the first character is
		     an ESC, ascii 033) that has been entered when  processing
		     a	KEYBD  trap (see Key Bindings below).  If the value is
		     changed as part of the trap action, then  the  new	 value
		     replaces the key (or key sequence) that caused the trap.
	      .sh.edcol
		     The  character  position of the cursor at the time of the
		     most recent KEYBD trap.
	      .sh.edmode
		     The value is set to ESC  when  processing	a  KEYBD  trap
		     while  in	vi insert mode.	 (See Vi Editing Mode  below.)
		     Otherwise, .sh.edmode is null  when  processing  a	 KEYBD
		     trap.
	      .sh.edtext
		     The  characters  in  the  input buffer at the time of the
		     most recent KEYBD trap.  The value is null when not  pro‐
		     cessing a KEYBD trap.
	      .sh.file
		     The  pathname  of the file than contains the current com‐
		     mand.
	      .sh.fun
		     The name of the current function that is being executed.
	      .sh.level
		     Set to the current function depth.	 This can  be  changed
		     inside a DEBUG trap and will set the context to the spec‐
		     ified level.
	      .sh.lineno
		     Set during a DEBUG trap to the line number for the caller
		     of each function.
	      .sh.match
		     An	 indexed  array which stores the most recent match and
		     sub-pattern matches  after	 conditional  pattern  matches
		     that match and after variables expansions using the oper‐
		     ators #, %, or /.	The 0-th element stores	 the  complete
		     match  and	 the  i-th.  element stores the i-th submatch.
		     The .sh.match variable becomes unset  when	 the  variable
		     that has expanded is assigned a new value.
	      .sh.math
		     Used  for	defining  arithmetic functions (see Arithmetic
		     evaluation below).	 and stores the list of	 user  defined
		     arithmetic functions.
	      .sh.name
		     Set to the name of the variable at the time that a disci‐
		     pline function is invoked.
	      .sh.subscript
		     Set to the name subscript of the  variable	 at  the  time
		     that a discipline function is invoked.
	      .sh.subshell
		     The current depth for subshells and command substitution.
	      .sh.value
		     Set to the value of the variable at the time that the set
		     or append discipline function is invoked.	 When  a  user
		     defined  arithmetic  function  is	invoked,  the value of
		     .sh.value is saved and .sh.value is set  to  long	double
		     precission	 floating  point.   .sh.value is restored when
		     the function returns.
	      .sh.version
		     Set to a value that identifies the version of this shell.
	      KSH_VERSION
		     A name reference to .sh.version.
	      LINENO The current line number within  the  script  or  function
		     being executed.
	      OLDPWD The previous working directory set by the cd command.
	      OPTARG The  value	 of  the last option argument processed by the
		     getopts built-in command.
	      OPTIND The index of the last option argument  processed  by  the
		     getopts built-in command.
	      PPID   The process number of the parent of the shell.
	      PWD    The present working directory set by the cd command.
	      RANDOM Each  time this variable is referenced, a random integer,
		     uniformly distributed between 0 and 32767, is  generated.
		     The  sequence  of	random	numbers	 can be initialized by
		     assigning a numeric value to RANDOM.
	      REPLY  This variable is set by the select statement and  by  the
		     read built-in command when no arguments are supplied.
	      SECONDS
		     Each time this variable is referenced, the number of sec‐
		     onds since shell invocation is returned.  If  this	 vari‐
		     able  is  assigned	 a value, then the value returned upon
		     reference will be the value that was  assigned  plus  the
		     number of seconds since the assignment.
	      SHLVL  An	 integer  variable  the	 is  incremented each time the
		     shell is invoked and is exported.	If SHLVL is not in the
		     environment when the shell is invoked, it is set to 1.

       The following variables are used by the shell:
	      CDPATH The search path for the cd command.
	      COLUMNS
		     If	 this variable is set, the value is used to define the
		     width of the edit window for the shell edit modes and for
		     printing select lists.
	      EDITOR If	 the  VISUAL  variable	is  not set, the value of this
		     variable will be checked for the  patterns	 as  described
		     with  VISUAL  below  and the corresponding editing option
		     (see Special Command set below) will be turned on.
	      ENV    If this variable is set, then parameter  expansion,  com‐
		     mand  substitution,  and arithmetic substitution are per‐
		     formed on the value  to  generate	the  pathname  of  the
		     script  that  will	 be executed when the shell is invoked
		     interactively (see Invocation below).  This file is typi‐
		     cally  used  for  alias  and  function  definitions.  The
		     default value is $HOME/.kshrc.  On systems that support a
		     system  wide   /etc/ksh.kshrc initialization file, if the
		     filename generated by the expansion of  ENV  begins  with
		     /./  or ././ the system wide initialization file will not
		     be executed.
	      FCEDIT Obsolete name for the default editor name	for  the  hist
		     command.  FCEDIT is not used when HISTEDIT is set.
	      FIGNORE
		     A	pattern that defines the set of filenames that will be
		     ignored when performing filename matching.
	      FPATH  The search path for function definitions.	 The  directo‐
		     ries  in  this path are searched for a file with the same
		     name as the function or command when a function with  the
		     -u	 attribute  is	referenced  and	 when a command is not
		     found.  If an executable file with the name of that  com‐
		     mand  is  found, then it is read and executed in the cur‐
		     rent environment.	Unlike	PATH,  the  current  directory
		     must be represented explicitly by .  rather than by adja‐
		     cent : characters or a beginning or ending :.
	      HISTCMD
		     Number of the current command in the history file.
	      HISTEDIT
		     Name for the default editor name for the hist command.
	      HISTFILE
		     If this variable is set when the shell is	invoked,  then
		     the  value	 is the pathname of the file that will be used
		     to	 store	the  command  history  (see  Command  Re-entry
		     below).
	      HISTSIZE
		     If	 this  variable is set when the shell is invoked, then
		     the number of previously entered commands that are acces‐
		     sible by this shell will be greater than or equal to this
		     number.  The default is 512.
	      HOME   The default argument (home directory) for the cd command.
	      IFS    Internal field separators, normally space, tab, and  new-
		     line  that	 are  used  to separate the results of command
		     substitution  or  parameter  expansion  and  to  separate
		     fields with the built-in command read.  The first charac‐
		     ter of the IFS variable is used to separate arguments for
		     the  "$∗"	substitution (see Quoting below).  Each single
		     occurrence of an IFS character in the string to be split,
		     that is not in the isspace character class, and any adja‐
		     cent characters in IFS that are in the isspace  character
		     class,  delimit  a	 field.	 One or more characters in IFS
		     that belong to the isspace	 character  class,  delimit  a
		     field.   In  addition,  if	 the  same  isspace  character
		     appears  consecutively  inside  IFS,  this	 character  is
		     treated  as  if it were not in the isspace class, so that
		     if IFS consists of two tab characters, then two  adjacent
		     tab characters delimit a null field.
	      JOBMAX This  variable  defines  the maximum number running back‐
		     ground jobs that can run at a time.  When this  limit  is
		     reached, the shell will wait for a job to complete before
		     staring a new job.
	      LANG   This variable determines the locale category for any cat‐
		     egory  not specifically selected with a variable starting
		     with LC_ or LANG.
	      LC_ALL This variable overrides the value of  the	LANG  variable
		     and any other LC_ variable.
	      LC_COLLATE
		     This  variable determines the locale category for charac‐
		     ter collation information.
	      LC_CTYPE
		     This variable determines the locale category for  charac‐
		     ter  handling  functions.	 It  determines	 the character
		     classes for pattern matching (see	File  Name  Generation
		     below).
	      LC_NUMERIC
		     This variable determines the locale category for the dec‐
		     imal point character.
	      LINES  If this variable is set, the value is used	 to  determine
		     the  column  length  for  printing	 select lists.	Select
		     lists will print vertically  until	 about	two-thirds  of
		     LINES lines are filled.
	      MAIL   If	 this  variable	 is set to the name of a mail file and
		     the MAILPATH variable is not set, then the shell  informs
		     the user of arrival of mail in the specified file.
	      MAILCHECK
		     This  variable specifies how often (in seconds) the shell
		     will check for changes in the modification time of any of
		     the  files	 specified  by the MAILPATH or MAIL variables.
		     The default value is 600  seconds.	  When	the  time  has
		     elapsed  the  shell  will	check  before issuing the next
		     prompt.
	      MAILPATH
		     A colon ( : ) separated list  of  file  names.   If  this
		     variable  is  set, then the shell informs the user of any
		     modifications to the specified files that	have  occurred
		     within the last MAILCHECK seconds.	 Each file name can be
		     followed by a ?  and a message that will be printed.  The
		     message will undergo parameter expansion, command substi‐
		     tution, and arithmetic substitution with the variable  $_
		     defined  as  the  name of the file that has changed.  The
		     default message is you have mail in $_.
	      PATH   The search path for commands (see Execution below).   The
		     user  may not change PATH if executing under rksh (except
		     in .profile).
	      PS1    The value of this	variable  is  expanded	for  parameter
		     expansion, command substitution, and arithmetic substitu‐
		     tion to define the primary prompt string which by default
		     is	 ``$''.	 The character !  in the primary prompt string
		     is replaced by the command number (see  Command  Re-entry
		     below).   Two successive occurrences of !	will produce a
		     single !  when the prompt string is printed.
	      PS2    Secondary prompt string, by default ``> ''.
	      PS3    Selection prompt string used within  a  select  loop,  by
		     default ``#? ''.
	      PS4    The  value	 of  this  variable  is expanded for parameter
		     evaluation, command substitution, and arithmetic  substi‐
		     tution  and precedes each line of an execution trace.  By
		     default, PS4 is ``+ ''.  In addition when PS4  is	unset,
		     the execution trace prompt is also ``+ ''.
	      SHELL  The pathname of the shell is kept in the environment.  At
		     invocation, if the basename  of  this  variable  is  rsh,
		     rksh,  or krsh, then the shell becomes restricted.	 If it
		     is pfsh or pfksh, then the shell becomes a profile	 shell
		     (see pfexec(1)).
	      TIMEFORMAT
		     The  value	 of  this parameter is used as a format string
		     specifying how the timing information for pipelines  pre‐
		     fixed  with  the  time reserved word should be displayed.
		     The % character introduces	 a  format  sequence  that  is
		     expanded  to a time value or other information.  The for‐
		     mat sequences and their meanings are as follows.
		     %%	       A literal %.
		     %[p][l]R  The elapsed time in seconds.
		     %[p][l]U  The number of CPU seconds spent in user mode.
		     %[p][l]S  The number of CPU seconds spent in system mode.
		     %P	       The CPU percentage, computed as (U + S) / R.

		     The brackets denote optional portions.  The optional p is
		     a	digit  specifying  the	precision, the number of frac‐
		     tional digits after a decimal point.  A value of 0 causes
		     no decimal point or fraction to be output.	 At most three
		     places after the decimal point can be  displayed;	values
		     of p greater than 3 are treated as 3.  If p is not speci‐
		     fied, the value 3 is used.

		     The optional l specifies a longer format, including hours
		     if	 greater  than	zero, minutes, and seconds of the form
		     HHhMMmSS.FFs.  The value of p determines whether  or  not
		     the fraction is included.

		     All  other	 characters  are  output  without change and a
		     trailing newline is added.	 If unset, the default	value,
		     $'\nreal\t%2lR\nuser\t%2lU\nsys%2lS',  is	used.	If the
		     value is null, no timing information is displayed.

	      TMOUT  If set to a value greater than zero, TMOUT	 will  be  the
		     default timeout value for the read built-in command.  The
		     select compound command terminates	 after	TMOUT  seconds
		     when input is from a terminal.  Otherwise, the shell will
		     terminate if a line is not entered within the  prescribed
		     number  of	 seconds while reading from a terminal.	 (Note
		     that the shell can be compiled with a maximum  bound  for
		     this value which cannot be exceeded.)

	      VISUAL If	 the  value  of	 this  variable	 matches  the  pattern
		     *[Vv][Ii]*, then the vi option (see Special  Command  set
		     below)  is	 turned	 on.  If the value matches the pattern
		     *gmacs* , the gmacs option is turned on.	If  the	 value
		     matches the pattern *macs*, then the emacs option will be
		     turned on.	 The value of VISUAL overrides	the  value  of
		     EDITOR.

       The  shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
       FCEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set  at
       all  by	the shell (although HOME is set by login(1)).  On some systems
       MAIL and SHELL are also set by login(1).

   Field Splitting.
       After parameter expansion and command substitution, the results of sub‐
       stitutions  are scanned for the field separator characters (those found
       in IFS) and split into distinct fields where such characters are found.
       Explicit	 null  fields  (""  or ′′) are retained.  Implicit null fields
       (those resulting from parameters that have no values or command substi‐
       tutions with no output) are removed.

       If the braceexpand (-B) option is set then each of the fields resulting
       from IFS are checked to see if they contain one or more	of  the	 brace
       patterns	 {*,*},	 {l1..l2} , {n1..n2} , {n1..n2% fmt} , {n1..n2 ..n3} ,
       or {n1..n2 ..n3%fmt} , where * represents any character, l1,l2 are let‐
       ters  and  n1,n2,n3 are signed numbers and fmt is a format specified as
       used by printf.	In each case, fields are  created  by  prepending  the
       characters  before  the	{  and appending the characters after the } to
       each of the strings generated by the characters between the  {  and  }.
       The  resulting  fields  are  checked to see if they have any brace pat‐
       terns.

       In the first form, a field is created for each string between { and  ,,
       between	, and ,, and between , and }.  The string represented by * can
       contain embedded matching { and } without quoting.  Otherwise,  each  {
       and } with * must be quoted.

       In  the	seconds form, l1 and l2 must both be either upper case or both
       be lower case characters in the C locale.  In this case a field is cre‐
       ated for each character from l1 thru l2.

       In  the remaining forms, a field is created for each number starting at
       n1 and continuing until it reaches n2 incrementing n1 by n3.  The cases
       where n3 is not specified behave as if n3 where 1 if n1<=n2 and -1 oth‐
       erwise.	If forms which specify %fmt any format flags, widths and  pre‐
       cisions	can  be	 specified  and	 fmt  can end in any of the specifiers
       cdiouxX.	 For  example,	{a,z}{1..5..3%02d}{b..c}x  expands  to	the  8
       fields, a01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx and z4cx.

   File Name Generation.
       Following  splitting, each field is scanned for the characters ∗, ?, (,
       and [ unless the -f option has been set.	 If one	 of  these  characters
       appears, then the word is regarded as a pattern.	 Each file name compo‐
       nent that contains any pattern character is  replaced  with  a  lexico‐
       graphically  sorted  set	 of  names  that matches the pattern from that
       directory.  If no file name is found that  matches  the	pattern,  then
       that  component of the filename is left unchanged unless the pattern is
       prefixed with ∼(N) in which case it is removed as described below.   If
       FIGNORE	is set, then each file name component that matches the pattern
       defined by the value of FIGNORE is ignored when generating the matching
       filenames.   The	 names .  and ..  are also ignored.  If FIGNORE is not
       set, the character .  at the start of each file name component will  be
       ignored unless the first character of the pattern corresponding to this
       component is the character .  itself.  Note, that  for  other  uses  of
       pattern matching the / and .  are not treated specially.

	      ∗	     Matches any string, including the null string.  When used
		     for filename expansion, if the globstar option is on, two
		     adjacent  ∗'s  by itself will match all files and zero or
		     more directories and subdirectories.  If followed by a  /
		     then only directories and subdirectories will match.
	      ?	     Matches any single character.
	      [...]  Matches  any  one	of the enclosed characters.  A pair of
		     characters separated by - matches any character lexically
		     between the pair, inclusive.  If the first character fol‐
		     lowing the opening [ is a !  or ^ then any character  not
		     enclosed  is matched.  A - can be included in the charac‐
		     ter set by putting it as the first or last character.
		     Within [ and ], character classes can be  specified  with
		     the  syntax [:class:] where class is one of the following
		     classes defined in the ANSI-C standard: (Note  that  word
		     is equivalent to alnum plus the character _.)
		     alnum  alpha  blank  cntrl	 digit graph lower print punct
		     space upper word xdigit
		     Within [ and ], an equivalence  class  can	 be  specified
		     with  the	syntax [=c=] which matches all characters with
		     the same primary collation weight (as defined by the cur‐
		     rent  locale) as the character c.	Within [ and ], [.sym‐
		     bol.]  matches the collating symbol symbol.
       A pattern-list is a list of one or more patterns	 separated  from  each
       other  with  a & or ⎪.  A & signifies that all patterns must be matched
       whereas ⎪ requires that only one pattern be  matched.   Composite  pat‐
       terns can be formed with one or more of the following sub-patterns:
	      ?(pattern-list)
		     Optionally matches any one of the given patterns.
	      *(pattern-list)
		     Matches zero or more occurrences of the given patterns.
	      +(pattern-list)
		     Matches one or more occurrences of the given patterns.
	      {n}(pattern-list)
		     Matches n occurrences of the given patterns.
	      {m,n}(pattern-list)
		     Matches  from  m  to n occurrences of the given patterns.
		     If m is omitted, 0 will be used.	If  n  is  omitted  at
		     least m occurrences will be matched.
	      @(pattern-list)
		     Matches exactly one of the given patterns.
	      !(pattern-list)
		     Matches anything except one of the given patterns.
       By  default, each pattern, or sub-pattern will match the longest string
       possible consistent with generating the longest overall match.  If more
       than  one  match is possible, the one starting closest to the beginning
       of the string will be chosen.   However, for each of the above compound
       patterns	 a  -  can be inserted in front of the ( to cause the shortest
       match to the specified pattern-list to be used.

       When pattern-list is contained within parentheses, the backslash	 char‐
       acter  \ is treated specially even when inside a character class.   All
       ANSI-C character escapes are recognized and match the specified charac‐
       ter.  In addition the following escape sequences are recognized:
	      \d     Matches any character in the digit class.
	      \D     Matches any character not in the digit class.
	      \s     Matches any character in the space class.
	      \S     Matches any character not in the space class.
	      \w     Matches any character in the word class.
	      \W     Matches any character not in the word class.

       A  pattern  of the form %(pattern-pair(s)) is a sub-pattern that can be
       used to match nested character expressions.  Each pattern-pair is a two
       character sequence which cannot contain & or ⎪.	The first pattern-pair
       specifies the starting and ending characters for the match.  Each  sub‐
       sequent	pattern-pair represents the beginning and ending characters of
       a nested group that will be skipped over	 when  counting	 starting  and
       ending  character  matches.  The behavior is unspecified when the first
       character of a pattern-pair is alpha-numeric except for the following:
	      D	     Causes the ending character to terminate the  search  for
		     this pattern without finding a match.
	      E	     Causes  the  ending  character  to	 be  interpreted as an
		     escape character.
	      L	     Causes the ending character to be interpreted as a	 quote
		     character causing all characters to be ignored when look‐
		     ing for a match.
	      Q	     Causes the ending character to be interpreted as a	 quote
		     character	causing	 all  characters other than any escape
		     character to be ignored when looking for a match.
       Thus, %({}Q"E\), matches characters starting at { until the matching  }
       is  found not counting any { or } that is inside a double quoted string
       or preceded by the escape character \.  Without	the  {}	 this  pattern
       matches any C language string.

       Each  sub-pattern in a composite pattern is numbered, starting at 1, by
       the location of the ( within the pattern.  The sequence \n, where n  is
       a  single  digit	 and \n comes after the n-th. sub-pattern, matches the
       same string as the sub-pattern itself.

       Finally a pattern can contain sub-patterns of the  form	∼(options:pat‐
       tern-list),  where  either  options  or	:pattern-list  can be omitted.
       Unlike the other compound patterns, these sub-patterns are not  counted
       in  the	numbered  sub-patterns.	 :pattern-list must be omitted for the
       upper-case options below.  If options is present, it can consist of one
       or more of the following:
	      +	     Enable the following options.  This is the default.
	      -	     Disable the following options.
	      E	     The  remainder  of	 the  pattern  uses  extended  regular
		     expression syntax like the egrep(1) command.
	      F	     The remainder of the  pattern  uses  fgrep(1)  expression
		     syntax.
	      G	     The  remainder  of the pattern uses basic regular expres‐
		     sion syntax like the grep(1) command.
	      K	     The remainder of the pattern uses shell  pattern  syntax.
		     This is the default.
	      N	     This  is  ignored.	  However, when it is the first letter
		     and is used with file name	 generation,  and  no  matches
		     occur, the file pattern expands to the empty string.
	      X	     The  remainder  of	 the  pattern  uses  augmented regular
		     expression syntax like the xgrep(1) command.
	      i	     Treat the match as case insensitive.
	      g	     File the longest match (greedy).  This is the default.
	      l	     Left anchor the pattern.  This is the default for K style
		     patterns.
	      r	     Right  anchor  the	 pattern.   This  is the default for K
		     style patterns.
       If both options and :pattern-list are specified, then the options apply
       only to	pattern-list.  Otherwise, these options remain in effect until
       they are disabled by a subsequent ∼(...) or at the end of the  sub-pat‐
       tern containing ∼(...).

   Quoting.
       Each of the metacharacters listed earlier (see Definitions above) has a
       special meaning to the shell and causes termination of  a  word	unless
       quoted.	 A character may be quoted (i.e., made to stand for itself) by
       preceding it with a \.  The pair \new-line is removed.  All  characters
       enclosed between a pair of single quote marks (′′) that is not preceded
       by a $ are quoted.  A single quote  cannot  appear  within  the	single
       quotes.	 A single quoted string preceded by an unquoted $ is processed
       as an ANSI-C string except for the following:
       \0     Causes the remainder of the string to be ignored.
       \E     Equivalent to the escape character (ascii 033),
       \e     Equivalent to the escape character (ascii 033),
       \cx    Expands to the character control-x.
       \C[.name.]
	      Expands to the collating element name.

       Inside double quote marks  (""),	 parameter  and	 command  substitution
       occur  and  \  quotes the characters \, `, ", and $.  A $ in front of a
       double quoted string will be ignored in the "C" or "POSIX" locale,  and
       may  cause the string to be replaced by a locale specific string other‐
       wise.  The meaning of $∗ and $@ is identical when not  quoted  or  when
       used  as	 a variable assignment value or as a file name.	 However, when
       used as a command argument, "$∗" is equivalent to "$1d$2d...", where  d
       is  the first character of the IFS variable, whereas "$@" is equivalent
       to "$1" "$2" ....  Inside grave quote marks (``), \ quotes the  charac‐
       ters \, `, and $.  If the grave quotes occur within double quotes, then
       \ also quotes the character ".

       The special meaning of reserved words or	 aliases  can  be  removed  by
       quoting	any  character of the reserved word.  The recognition of func‐
       tion names or built-in command names listed below cannot be altered  by
       quoting them.

   Arithmetic Evaluation.
       The  shell  performs arithmetic evaluation for arithmetic substitution,
       to evaluate an arithmetic command, to evaluate an  indexed  array  sub‐
       script,	and  to	 evaluate arguments to the built-in commands shift and
       let.  Evaluations are performed using double precision  floating	 point
       arithmetic  or  long  double  precision floating point for systems that
       provide this data type.	Floating point	constants  follow  the	ANSI-C
       programming  language  floating	point  conventions.  Integer constants
       follow the ANSI-C programming  language	integer	 constant  conventions
       although	 only single byte character constants are recognized and char‐
       acter casts are not recognized.	In addition constants can  be  of  the
       form [base#]n where base is a decimal number between two and sixty-four
       representing the arithmetic base and n is a number in that  base.   The
       digits  above  9	 are  represented by the lower case letters, the upper
       case letters, @, and _ respectively.  For bases less than or  equal  to
       36, upper and lower case characters can be used interchangeably.

       An arithmetic expression uses the same syntax, precedence, and associa‐
       tivity of expression as the C language.	All the C  language  operators
       that  apply to floating point quantities can be used.  In addition, the
       operator ** can be used for exponentiation.  It has  higher  precedence
       than  multiplication  and  is  left associative.	 In addition, when the
       value of an arithmetic variable or sub-expression can be represented as
       a  long	integer,  all  C language integer arithmetic operations can be
       performed.  Variables can be referenced by name	within	an  arithmetic
       expression  without using the parameter expansion syntax.  When a vari‐
       able is referenced, its value is evaluated as an arithmetic expression.

       Any of the following math library functions that	 are  in  the  C  math
       library can be used within an arithmetic expression:

       abs  acos  acosh asin asinh atan atan2 atanh cbrt copysign cos cosh erf
       erfc exp exp2 expm1 fabs fdim finite floor fma  fmax  fmin  fmod	 hypot
       ilogb int isinf isnan j0 j1 jn lgamma log log2 logb nearbyint nextafter
       nexttoward pow remainder rint round sin sinh sqrt tan tanh tgamma trunc
       y0 y1 yn In addition, arithmetic functions can be define as shell func‐
       tions with a variant of the function name syntax,

       function .sh.math.name ident ... { list ;}
	      where name is the function name used in the  arithmetic  expres‐
	      sion  and each identifier, ident is a name reference to the long
	      double  precission  floating  point  argument.   The  value   of
	      .sh.value	 when  the function returns is the value of this func‐
	      tion.  User defined functions can take up	 to  3	arguments  and
	      override C math library functions.

       An internal representation of a variable as a double precision floating
       point can be specified with the -E [n], -F [n], or -X [n] option of the
       typeset	special	 built-in command.  The -E option causes the expansion
       of the value to be represented using scientific	notation  when	it  is
       expanded.  The optional option argument n defines the number of signif‐
       icant figures.  The -F option causes the expansion to be represented as
       a floating decimal number when it is expanded.  The -X option cause the
       expansion to be represented using the %a format defined	by  ISO	 C-99.
       The  optional  option argument n defines the number of places after the
       decimal (or radix) point in this case.

       An internal integer representation of a variable can be specified  with
       the  -i	[n]  option  of	 the  typeset  special	built-in command.  The
       optional option argument n specifies an arithmetic base to be used when
       expanding the variable.	If you do not specify an arithmetic base, base
       10 will be used.

       Arithmetic evaluation is performed on the value of each assignment to a
       variable	 with  the  -E, -F, -X, or -i attribute.  Assigning a floating
       point number to a variable whose type is an integer  causes  the	 frac‐
       tional part to be truncated.

   Prompting.
       When  used interactively, the shell prompts with the value of PS1 after
       expanding it for parameter expansion, command substitution, and	arith‐
       metic substitution, before reading a command.  In addition, each single
       !  in the prompt is replaced by the command number.  A !!  is  required
       to place !  in the prompt.  If at any time a new-line is typed and fur‐
       ther input is needed to complete a command, then the  secondary	prompt
       (i.e., the value of PS2) is issued.

   Conditional Expressions.
       A  conditional  expression is used with the [[ compound command to test
       attributes of files and to compare strings.  Field splitting  and  file
       name generation are not performed on the words between [[ and ]].  Each
       expression can be constructed from one or more of the  following	 unary
       or binary expressions:
       string True, if string is not null.
       -a file
	      Same as -e below.	 This is obsolete.
       -b file
	      True, if file exists and is a block special file.
       -c file
	      True, if file exists and is a character special file.
       -d file
	      True, if file exists and is a directory.
       -e file
	      True, if file exists.
       -f file
	      True, if file exists and is an ordinary file.
       -g file
	      True, if file exists and it has its setgid bit set.
       -k file
	      True, if file exists and it has its sticky bit set.
       -n string
	      True, if length of string is non-zero.
       -o ?option
	      True, if option named option is a valid option name.
       -o option
	      True, if option named option is on.
       -p file
	      True, if file exists and is a fifo special file or a pipe.
       -r file
	      True, if file exists and is readable by current process.
       -s file
	      True, if file exists and has size greater than zero.
       -t fildes
	      True,  if	 file  descriptor number fildes is open and associated
	      with a terminal device.
       -u file
	      True, if file exists and it has its setuid bit set.
       -w file
	      True, if file exists and is writable by current process.
       -x file
	      True, if file exists and is executable by current	 process.   If
	      file exists and is a directory, then true if the current process
	      has permission to search in the directory.
       -z string
	      True, if length of string is zero.
       -L file
	      True, if file exists and is a symbolic link.
       -h file
	      True, if file exists and is a symbolic link.
       -N file
	      True, if file exists and the modification time is	 greater  than
	      the last access time.
       -O file
	      True,  if	 file  exists and is owned by the effective user id of
	      this process.
       -G file
	      True, if file exists and its group matches the  effective	 group
	      id of this process.
       -S file
	      True, if file exists and is a socket.
       file1 -nt file2
	      True, if file1 exists and file2 does not, or file1 is newer than
	      file2.
       file1 -ot file2
	      True, if file2 exists and file1 does not, or file1 is older than
	      file2.
       file1 -ef file2
	      True, if file1 and file2 exist and refer to the same file.
       string == pattern
	      True,  if	 string	 matches  pattern.  Any part of pattern can be
	      quoted to cause it to be matched as a string.  With a successful
	      match  to	 a  pattern, the .sh.match array variable will contain
	      the match and sub-pattern matches.
       string = pattern
	      Same as == above, but is obsolete.
       string != pattern
	      True, if string does not match pattern.  When the string matches
	      the  pattern the .sh.match array variable will contain the match
	      and sub-pattern matches.
       string =∼ ere
	      True if string matches the  pattern  ∼(E)ere  where  ere	is  an
	      extended regular expression.
       string1 < string2
	      True,  if	 string1  comes before string2 based on ASCII value of
	      their characters.
       string1 > string2
	      True, if string1 comes after string2 based  on  ASCII  value  of
	      their characters.
       The following obsolete arithmetic comparisons are also permitted:
       exp1 -eq exp2
	      True, if exp1 is equal to exp2.
       exp1 -ne exp2
	      True, if exp1 is not equal to exp2.
       exp1 -lt exp2
	      True, if exp1 is less than exp2.
       exp1 -gt exp2
	      True, if exp1 is greater than exp2.
       exp1 -le exp2
	      True, if exp1 is less than or equal to exp2.
       exp1 -ge exp2
	      True, if exp1 is greater than or equal to exp2.

       In  each	 of  the  above expressions, if file is of the form /dev/fd/n,
       where n is an integer, then the test is applied to the open file	 whose
       descriptor number is n.

       A compound expression can be constructed from these primitives by using
       any of the following, listed in decreasing order of precedence.
       (expression)
	      True, if expression is true.  Used to group expressions.
       ! expression
	      True if expression is false.
       expression1 && expression2
	      True, if expression1 and expression2 are both true.
       expression1 ⎪⎪ expression2
	      True, if either expression1 or expression2 is true.

   Input/Output.
       Before a command is executed, its input and output  may	be  redirected
       using  a	 special notation interpreted by the shell.  The following may
       appear anywhere in a simple-command or may precede or follow a  command
       and  are	 not  passed on to the invoked command.	 Command substitution,
       parameter expansion, and arithmetic substitution occur before  word  or
       digit  is used except as noted below.  File name generation occurs only
       if the shell is interactive and the  pattern  matches  a	 single	 file.
       Field splitting is not performed.

       In  each	 of  the  following  redirections,  if	file  is  of  the form
       /dev/sctp/host/port, /dev/tcp/host/port, or  /dev/udp/host/port,	 where
       host is a hostname or host address, and port is a service given by name
       or an integer port number, then the redirection attempts to make a tcp,
       sctp or udp connection to the corresponding socket.

       No  intervening	space is allowed between the characters of redirection
       operators.

       <word	     Use file word as standard input (file descriptor 0).

       >word	     Use file word as standard output (file descriptor 1).  If
		     the  file does not exist then it is created.  If the file
		     exists, and the noclobber option is on,  this  causes  an
		     error; otherwise, it is truncated to zero length.

       >|word	     Sames  as	>,  except  that  it  overrides	 the noclobber
		     option.

       >;word	     Write output to a temporary file.	If  the	 command  com‐
		     pletes  successfully rename it to word, otherwise, delete
		     the temporary file.   >;word  cannot  be  used  with  the
		     exec(2).  built-in.

       >>word	     Use  file	word  as standard output.  If the file exists,
		     then output is appended to it (by first  seeking  to  the
		     end-of-file); otherwise, the file is created.

       <>word	     Open  file	 word for reading and writing as standard out‐
		     put.

       <>;word	     The same as <>word except that if the  command  completes
		     successfully,  word is truncated to the offset at command
		     completion.  <>;word cannot be  used  with	 the  exec(2).
		     built-in.

       <<[-]word     The  shell input is read up to a line that is the same as
		     word after any quoting has been removed, or to an end-of-
		     file.   No	 parameter substitution, command substitution,
		     arithmetic substitution or file name generation  is  per‐
		     formed  on	 word.	The resulting document, called a here-
		     document, becomes the standard input.  If	any  character
		     of	 word is quoted, then no interpretation is placed upon
		     the characters  of	 the  document;	 otherwise,  parameter
		     expansion, command substitution, and arithmetic substitu‐
		     tion occur, \new-line is ignored, and \ must be  used  to
		     quote  the	 characters  \, $, `.  If - is appended to <<,
		     then all leading tabs are stripped from word and from the
		     document.	 If  #	is appended to <<, then leading spaces
		     and tabs will be stripped off the first line of the docu‐
		     ment and up to an equivalent indentation will be stripped
		     from the remaining lines and from word.  A	 tab  stop  is
		     assumed  to  occur at every 8 columns for the purposes of
		     determining the indentation.

       <<<word	     A short form of here document in which word  becomes  the
		     contents  of the here-document after any parameter expan‐
		     sion, command substitution, and  arithmetic  substitution
		     occur.

       <&digit	     The  standard  input  is  duplicated from file descriptor
		     digit (see dup(2)).  Similarly for	 the  standard	output
		     using >&digit.

       <&digit-	     The  file	descriptor given by digit is moved to standard
		     input.  Similarly for the standard output using >&digit-.

       <&-	     The standard input is closed.  Similarly for the standard
		     output using >&-.

       <&p	     The input from the co-process is moved to standard input.

       >&p	     The output to the co-process is moved to standard output.

       <#((expr))    Evaluate  arithmetic  expression  expr  and position file
		     descriptor 0 to the resulting value bytes from the	 start
		     of	 the  file.  The variables CUR and EOF evaluate to the
		     current offset and end-of-file offset  respectively  when
		     evaluating expr.

       >#((offset))  The same as <# except applies to file descriptor 1.

       <#pattern     Seeks  forward to the beginning of the next line contain‐
		     ing pattern.

       <##pattern    The same as <# except that the portion of the  file  that
		     is skipped is copied to standard output.

       If  one of the above is preceded by a digit, with no intervening space,
       then the file descriptor number referred to is that  specified  by  the
       digit (instead of the default 0 or 1).  If one of the above, other than
       >&- and the ># and <# forms, is preceded by {varname} with no interven‐
       ing  space,  then a file descriptor number > 10 will be selected by the
       shell and stored in the variable varname.  If >&- or the any of the  >#
       and  <# forms is preceded by {varname} the value of varname defines the
       file descriptor to close or position.  For example:

	      ... 2>&1

       means file descriptor 2 is to be opened for writing as a	 duplicate  of
       file descriptor 1 and

	      exec {n}<file

       means  open  file  named file for reading and store the file descriptor
       number in variable n.

       The order in which redirections	are  specified	is  significant.   The
       shell  evaluates	 each  redirection  in	terms of the (file descriptor,
       file) association at the time of evaluation.  For example:

	      ... 1>fname 2>&1

       first associates file descriptor 1 with file fname.  It then associates
       file descriptor 2 with the file associated with file descriptor 1 (i.e.
       fname).	If the order of redirections were reversed, file descriptor  2
       would  be  associated with the terminal (assuming file descriptor 1 had
       been) and then file descriptor 1 would be associated with file fname.

       If a command is followed by & and job control is not active,  then  the
       default	standard  input	 for  the command is the empty file /dev/null.
       Otherwise, the environment for the execution of a command contains  the
       file  descriptors  of  the  invoking  shell as modified by input/output
       specifications.

   Environment.
       The environment (see environ(7)) is a list of name-value pairs that  is
       passed  to  an  executed	 program  in the same way as a normal argument
       list.  The names must be	 identifiers  and  the	values	are  character
       strings.	 The shell interacts with the environment in several ways.  On
       invocation, the shell scans the environment and creates a variable  for
       each  name  found, giving it the corresponding value and attributes and
       marking it export.  Executed commands inherit the environment.  If  the
       user  modifies the values of these variables or creates new ones, using
       the export or typeset -x commands, they become part of the environment.
       The  environment	 seen  by any executed command is thus composed of any
       name-value pairs originally inherited by the shell, whose values may be
       modified	 by  the current shell, plus any additions which must be noted
       in export or typeset -x commands.

       The environment for any simple-command or function may be augmented  by
       prefixing it with one or more variable assignments.  A variable assign‐
       ment argument is a word of the form identifier=value.  Thus:

	      TERM=450 cmd args			 and
	      (export TERM; TERM=450; cmd args)

       are equivalent (as far as the  above  execution	of  cmd	 is  concerned
       except for special built-in commands listed below - those that are pre‐
       ceded with a dagger).

       If the obsolete -k option is set, all variable assignment arguments are
       placed  in  the environment, even if they occur after the command name.
       The following first prints a=b c and then c:

	      echo a=b c
	      set -k
	      echo a=b c
       This feature is intended for use with scripts written  for  early  ver‐
       sions  of the shell and its use in new scripts is strongly discouraged.
       It is likely to disappear someday.

   Functions.
       For historical reasons, there are two ways  to  define  functions,  the
       name()  syntax  and the function name syntax, described in the Commands
       section above.  Shell functions are  read  in  and  stored  internally.
       Alias names are resolved when the function is read.  Functions are exe‐
       cuted like commands with the arguments passed as positional parameters.
       (See Execution below.)

       Functions  defined  by the function name syntax and called by name exe‐
       cute in the same process as the caller and share all files and  present
       working	directory  with	 the  caller.	Traps caught by the caller are
       reset to their default action inside the function.   A  trap  condition
       that  is	 not  caught or ignored by the function causes the function to
       terminate and the condition to be passed on to the caller.  A  trap  on
       EXIT set inside a function is executed in the environment of the caller
       after the function completes.  Ordinarily, variables are shared between
       the  calling  program  and  the function.  However, the typeset special
       built-in command used within a function defines local  variables	 whose
       scope  includes	the current function.  They can be passed to functions
       that they call in the variable assignment list that precedes  the  call
       or  as  arguments  passed  as name references.  Errors within functions
       return control to the caller.

       Functions defined with the name() syntax and functions defined with the
       function	 name syntax that are invoked with the .  special built-in are
       executed in the caller's environment and share all variables and	 traps
       with  the  caller.   Errors  within these function executions cause the
       script that contains them to abort.

       The special built-in command return is used  to	return	from  function
       calls.

       Function	 names	can  be listed with the -f or +f option of the typeset
       special built-in command.  The text of functions, when available,  will
       also  be listed with -f.	 Functions can be undefined with the -f option
       of the unset special built-in command.

       Ordinarily, functions are unset when the shell executes a shell script.
       Functions  that	need  to be defined across separate invocations of the
       shell should be placed in a directory and  the  FPATH  variable	should
       contain	the name of this directory.  They may also be specified in the
       ENV file.

   Discipline Functions.
       Each variable can have zero or  more  discipline	 functions  associated
       with  it.   The	shell  initially understands the discipline names get,
       set, append, and unset but can be added when defining  new  types.   On
       most  systems  others  can  be  added at run time via the C programming
       interface extension provided by the builtin built-in utility.   If  the
       get  discipline	is  defined for a variable, it is invoked whenever the
       given variable is referenced.  If the variable .sh.value is assigned  a
       value  inside  the  discipline  function,  the referenced variable will
       evaluate to this value instead.	If the set discipline is defined for a
       variable,  it  is  invoked  whenever  the  given variable is assigned a
       value.  If the append discipline is  defined  for  a  variable,	it  is
       invoked	whenever a value is appended to the given variable.  The vari‐
       able .sh.value is given the value of the variable before	 invoking  the
       discipline,  and	 the  variable will be assigned the value of .sh.value
       after the discipline completes.	If .sh.value is unset inside the  dis‐
       cipline,	 then  that  value  is	unchanged.  If the unset discipline is
       defined for a variable, it is invoked whenever the  given  variable  is
       unset.	The  variable  will not be unset unless it is unset explicitly
       from within this discipline function.

       The variable .sh.name contains the name of the variable for  which  the
       discipline  function  is	 called, .sh.subscript is the subscript of the
       variable, and .sh.value will contain the value  being  assigned	inside
       the  set	 discipline  function.	 The  variable _ is a reference to the
       variable including the subscript	 if  any.   For	 the  set  discipline,
       changing	 .sh.value will change the value that gets assigned.  Finally,
       the expansion ${var.name}, when name is the name of a  discipline,  and
       there is no variable of this name, is equivalent to the command substi‐
       tution ${ var.name;}.

   Name Spaces.
       Commands and functions that are executed as  part  of  the  list	 of  a
       namespace  command  that	 modify variables or create new ones, create a
       new variable whose name is the name of the name space as given by iden‐
       tifier  preceded	 by  ..	  When a variable whose name is name is refer‐
       enced, it is first searched for using .identifier.name.	 Similarly,  a
       function	 defined  by  a command in the namespace list is created using
       the name space name  preceded by a ..

       When  the list of a namespace command contains a namespace command, the
       names  of  variable and functions that are created consist of the vari‐
       able or function name preceded by the list of identifiers each preceded
       by ..

       Outside	of a name space, a variable or function created inside a names
       space can be referenced by preceding it with the name space name.

       By default, variables staring with .sh are in the sh name space.

   Type Variables.
       Typed variables provide a way to create data structure and objects.   A
       type  can  be  defined either by a shared library, by the enum built-in
       command described below, or by using the new -T option of  the  typeset
       built-in command.  With the -T option of typeset, the type name, speci‐
       fied as an option argument to -T,  is  set  with	 a  compound  variable
       assignment  that	 defines  the  type.   Function definitions can appear
       inside the compound variable assignment	and  these  become  discipline
       functions  for  this  type  and	can  be	 invoked  or redefined by each
       instance of the type.  The function name create is  treated  specially.
       It  is invoked for each instance of the type that is created but is not
       inherited and cannot be redefined for each instance.

       When a type is defined a special	 built-in  command  of	that  name  is
       added.	These  built-ins  are declaration commands and follow the same
       expansion rules as all the special built-in commands defined below that
       are  preceded  by  ††.	These commands can subsequently be used inside
       further type definitions.  The man page for these commands can be  gen‐
       erated  by  using  the  --man  option  or  any  of the other -- options
       described with getopts.	The -r, -a, -A, -h, and -S options of  typeset
       are permitted with each of these new built-ins.

       An  instance of a type is created by invoking the type name followed by
       one or more instance names.  Each instance of the type  is  initialized
       with  a	copy  of  the  sub-variables except for sub-variables that are
       defined with the -S option.  Variables defined with the -S  are	shared
       by  all	instances  of the type.	 Each instance can change the value of
       any sub-variable and can also define new discipline  functions  of  the
       same names as those defined by the type definition as well as any stan‐
       dard discipline names.  No additional sub-variables can be defined  for
       any instance.

       When defining a type, if the value of a sub-variable is not set and the
       -r attribute is specified, it causes the sub-variable to be a  required
       sub-variable.   Whenever an instance of a type is created, all required
       sub-variables must be specified.	 These sub-variables  become  readonly
       in each instance.

       When  unset  is	invoked	 on  a	sub-variable within a type, and the -r
       attribute has not been specified for this field, the value is reset  to
       the  default value associative with the type.  Invoking unset on a type
       instance not contained within another type  deletes  all	 sub-variables
       and the variable itself.

       A type definition can be derived from another type definition by defin‐
       ing the first sub-variable name as _ and defining its type as the  base
       type.   Any  remaining  definitions will be additions and modifications
       that apply to the new type.  If the new type name is the same  is  that
       of  the base type, the type will be replaced and the original type will
       no longer be accessible.

       The typeset command with the -T and no option argument or operands will
       write  all  the type definitions to standard output in a form that that
       can be read in to create all they types.

   Jobs.
       If the monitor option of the set command is turned on,  an  interactive
       shell associates a job with each pipeline.  It keeps a table of current
       jobs, printed by the jobs command, and assigns them small integer  num‐
       bers.   When a job is started asynchronously with &, the shell prints a
       line which looks like:

	    [1] 1234

       indicating that the job which was started asynchronously was job number
       1 and had one (top-level) process, whose process id was 1234.

       This  paragraph	and the next require features that are not in all ver‐
       sions of UNIX and may not apply.	 If you are running a job and wish  to
       do something else you may hit the key ^Z (control-Z) which sends a STOP
       signal to the current job.  The shell will then normally indicate  that
       the  job	 has  been  `Stopped', and print another prompt.  You can then
       manipulate the state of this job, putting it in the background with the
       bg  command,  or	 run some other commands and then eventually bring the
       job back into the foreground with the  foreground  command  fg.	 A  ^Z
       takes  effect immediately and is like an interrupt in that pending out‐
       put and unread input are discarded when it is typed.

       A job being run in the background will stop if it tries	to  read  from
       the  terminal.  Background jobs are normally allowed to produce output,
       but this can be disabled by giving the command stty tostop.  If you set
       this  tty  option, then background jobs will stop when they try to pro‐
       duce output like they do when they try to read input.

       A job pool is a collection of jobs started with list & associated  with
       a name.

       There  are  several  ways  to refer to jobs in the shell.  A job can be
       referred to by the process id of any process of the job or  by  one  of
       the following:
       %number
	      The job with the given number.
       pool   All the jobs in the job pool named by pool.
       pool.number
	      The job number number in the job pool named by pool.
       %string
	      Any job whose command line begins with string.
       %?string
	      Any job whose command line contains string.
       %%     Current job.
       %+     Equivalent to %%.
       %-     Previous	job.   In addition, unless noted otherwise, wherever a
	      job can be specified, the name of a background job pool  can  be
	      used to represet all the jobs in that pool.

       The shell learns immediately whenever a process changes state.  It nor‐
       mally informs you whenever a job becomes blocked	 so  that  no  further
       progress is possible, but only just before it prints a prompt.  This is
       done so that it does not	 otherwise  disturb  your  work.   The	notify
       option  of  the	set command causes the shell to print these job change
       messages as soon as they occur.

       When the monitor option is on, each background job that completes trig‐
       gers any trap set for CHLD.

       When  you try to leave the shell while jobs are running or stopped, you
       will be warned that `You have stopped(running) jobs.'  You may use  the
       jobs  command  to  see  what  they are.	If you immediately try to exit
       again, the shell will not warn you a second time, and the stopped  jobs
       will be terminated.  When a login shell receives a HUP signal, it sends
       a HUP signal to each job that has not been  disowned  with  the	disown
       built-in command described below.

   Signals.
       The INT and QUIT signals for an invoked command are ignored if the com‐
       mand is followed by & and the monitor option is not active.  Otherwise,
       signals have the values inherited by the shell from its parent (but see
       also the trap built-in command below).

   Execution.
       Each time a command is read, the above substitutions are	 carried  out.
       If the command name matches one of the Special Built-in Commands listed
       below, it is executed within the current shell process.	Next, the com‐
       mand  name is checked to see if it matches a user defined function.  If
       it does, the positional parameters are saved  and  then	reset  to  the
       arguments  of  the  function  call.  A function is also executed in the
       current shell process.  When the function completes or issues a return,
       the  positional parameter list is restored.  For functions defined with
       the function name syntax, any trap set on EXIT within the  function  is
       executed.   The	exit value of a function is the value of the last com‐
       mand executed.  If a command name is not a special built-in command  or
       a  user defined function, but it is one of the built-in commands listed
       below, it is executed in the current shell process.

       The shell variable PATH defines the search path for the directory  con‐
       taining	the  command.	Alternative directory names are separated by a
       colon (:).   The	 default  path	is  /bin:/usr/bin:  (specifying	 /bin,
       /usr/bin, and the current directory in that order).  The current direc‐
       tory can be specified by two or more adjacent colons, or by a colon  at
       the  beginning or end of the path list.	If the command name contains a
       /, then the search path is not used.  Otherwise, each directory in  the
       path is searched for an executable file of the given name that is not a
       directory.  If found, and if the	 shell	determines  that  there	 is  a
       built-in	 version  of a command corresponding to a given pathname, this
       built-in is invoked in the current process.  If found, and this	direc‐
       tory  is	 also  contained in the value of the FPATH variable, then this
       file is loaded into the current shell environment as  if	 it  were  the
       argument to the . command except that only preset aliases are expanded,
       and a function of the given name is executed as	described  above.   If
       not  found, and the file .paths is found, and this file contains a line
       of the form FPATH=path where path names an existing directory, and this
       directory  contains  a file of the given name, then this file is loaded
       into the current shell environment as if it were the argument to the  .
       special	built-in command and a function of the given name is executed.
       Otherwise, if found, a process is created and an	 attempt  is  made  to
       execute the command via exec(2).

       When  an	 executable  is	 found,	 the directory where it is found in is
       searched for a file named .paths.  If this file is found	 and  it  con‐
       tains  a line of the form BUILTIN_LIB=value , then the library named by
       value will be searched for as if it were an option argument to  builtin
       -f,  and	 if  it contains a built-in of the specified name this will be
       executed instead of a command by this name.  Otherwise, if this file is
       found  and  it  contains	 a line of the form name=value in the first or
       second line, then the environment variable name is modified by prepend‐
       ing  the	 directory specified by value to the directory list.  If value
       is not an absolute directory, then it specifies a directory relative to
       the  directory that the executable was found.  If the environment vari‐
       able name does not already exist it will be added  to  the  environment
       list for the specified command.

       If  the	file  has  execute  permission but is not an a.out file, it is
       assumed to be a file containing shell commands.	A  separate  shell  is
       spawned	to  read  it.	All non-exported variables are removed in this
       case.  If the shell command file doesn't have read  permission,	or  if
       the  setuid and/or setgid bits are set on the file, then the shell exe‐
       cutes an agent whose job it is to set up the  permissions  and  execute
       the  shell  with the shell command file passed down as an open file.  A
       parenthesized command is executed in a sub-shell without removing  non-
       exported variables.

   Command Re-entry.
       The  text  of  the  last HISTSIZE (default 512) commands entered from a
       terminal device is saved in a history file.  The file $HOME/.sh_history
       is  used if the HISTFILE variable is not set or if the file it names is
       not writable.  A shell can  access  the	commands  of  all  interactive
       shells which use the same named HISTFILE.  The built-in command hist is
       used to list or edit a portion of this file.  The portion of  the  file
       to be edited or listed can be selected by number or by giving the first
       character or characters of the command.	A single command or  range  of
       commands	 can be specified.  If you do not specify an editor program as
       an argument to hist then the value of the variable  HISTEDIT  is	 used.
       If  HISTEDIT is unset, the obsolete variable FCEDIT is used.  If FCEDIT
       is not defined, then /bin/ed is used.  The edited command(s) is printed
       and  re-executed	 upon leaving the editor unless you quit without writ‐
       ing.  The -s option (and in obsolete versions, the editor  name	-)  is
       used  to skip the editing phase and to re-execute the command.  In this
       case a substitution parameter of the form old=new can be used to modify
       the  command  before  execution.	 For example, with the preset alias r,
       which is aliased to ′hist -s′, typing `r bad=good  c'  will  re-execute
       the  most  recent command which starts with the letter c, replacing the
       first occurrence of the string bad with the string good.

   In-line Editing Options.
       Normally, each command line entered from a terminal  device  is	simply
       typed  followed by a new-line (`RETURN' or `LINE FEED').	 If either the
       emacs, gmacs, or vi option is active, the user  can  edit  the  command
       line.   To  be  in  either  of  these  edit modes set the corresponding
       option.	An editing option is automatically selected each time the VIS‐
       UAL  or	EDITOR	variable is assigned a value ending in either of these
       option names.

       The editing features require that the user's terminal  accept  `RETURN'
       as  carriage return without line feed and that a space (` ') must over‐
       write the current character on the screen.

       Unless the multiline option is on, the editing modes implement  a  con‐
       cept  where  the	 user is looking through a window at the current line.
       The window width is the value of COLUMNS if it  is  defined,  otherwise
       80.   If	 the window width is too small to display the prompt and leave
       at least 8 columns to enter input, the prompt  is  truncated  from  the
       left.  If the line is longer than the window width minus two, a mark is
       displayed at the end of the window to notify the user.  As  the	cursor
       moves  and  reaches  the	 window boundaries the window will be centered
       about the cursor.  The mark is a > (<, *) if the line  extends  on  the
       right (left, both) side(s) of the window.

       The  search  commands  in  each edit mode provide access to the history
       file.  Only strings are matched, not patterns, although a leading ^  in
       the  string  restricts the match to begin at the first character in the
       line.

       Each of the edit modes has an operation to list the files  or  commands
       that match a partially entered word.  When applied to the first word on
       the line, or the first word after a ;, ⎪, &, or (, and  the  word  does
       not  begin  with	 ∼ or contain a /, the list of aliases, functions, and
       executable commands defined by the PATH variable that could  match  the
       partial word is displayed.  Otherwise, the list of files that match the
       given word is displayed.	 If the partially entered word does  not  con‐
       tain  any  file expansion characters, a * is appended before generating
       these lists.  After displaying the generated list, the  input  line  is
       redrawn.	  These	 operations  are  called command name listing and file
       name listing, respectively.  There are additional operations,  referred
       to  as  command name completion and file name completion, which compute
       the list of matching commands or files, but  instead  of	 printing  the
       list,  replace  the current word with a complete or partial match.  For
       file name completion, if the match is unique, a / is  appended  if  the
       file is a directory and a space is appended if the file is not a direc‐
       tory.  Otherwise, the longest common prefix for all the matching	 files
       replaces	 the  word.   For command name completion, only the portion of
       the file names after the last / are used to find	 the  longest  command
       prefix.	 If  only  a single name matches this prefix, then the word is
       replaced with the command name followed by a space.  When using	a  tab
       for  completion	that  does  not yield a unique match, a subsequent tab
       will provide a numbered list  of	 matching  alternatives.   A  specific
       selection  can  be  made by entering the selection number followed by a
       tab.

   Key Bindings.
       The KEYBD trap can be used to intercept keys  as	 they  are  typed  and
       change  the  characters that are actually seen by the shell.  This trap
       is executed after each character (or sequence of	 characters  when  the
       first  character is ESC) is entered while reading from a terminal.  The
       variable .sh.edchar contains the character or character sequence	 which
       generated  the  trap.   Changing	 the  value  of .sh.edchar in the trap
       action causes the shell to behave as if the new value were entered from
       the keyboard rather than the original value.

       The  variable .sh.edcol is set to the input column number of the cursor
       at the time of the input.  The variable .sh.edmode is set to  ESC  when
       in  vi  insert  mode  (see below) and is null otherwise.	 By prepending
       ${.sh.editmode} to a value assigned to .sh.edchar  it  will  cause  the
       shell to change to control mode if it is not already in this mode.

       This trap is not invoked for characters entered as arguments to editing
       directives, or while reading input for a character search.

   Emacs Editing Mode.
       This mode is entered by enabling either the emacs or gmacs option.  The
       only  difference between these two modes is the way they handle ^T.  To
       edit, the user moves the cursor to the  point  needing  correction  and
       then inserts or deletes characters or words as needed.  All the editing
       commands are control characters or escape sequences.  The notation  for
       control	characters  is caret (^) followed by the character.  For exam‐
       ple, ^F is the notation for control F.  This is entered	by  depressing
       `f'  while  holding  down the `CTRL' (control) key.  The `SHIFT' key is
       not depressed.  (The notation ^?	 indicates the DEL (delete) key.)

       The notation for escape sequences is M- followed by a  character.   For
       example,	 M-f  (pronounced  Meta f) is entered by depressing ESC (ascii
       033) followed by `f'.  (M-F would be the notation for ESC  followed  by
       `SHIFT' (capital) `F'.)

       All  edit  commands operate from any place on the line (not just at the
       beginning).  Neither the `RETURN' nor the `LINE FEED'  key  is  entered
       after edit commands except when noted.

       ^F	 Move cursor forward (right) one character.
       M-[C	 Move cursor forward (right) one character.
       M-f	 Move  cursor forward one word.	 (The emacs editor's idea of a
		 word is a string of characters consisting  of	only  letters,
		 digits and underscores.)
       ^B	 Move cursor backward (left) one character.
       M-[D	 Move cursor backward (left) one character.
       M-b	 Move cursor backward one word.
       ^A	 Move cursor to start of line.
       M-[H	 Move cursor to start of line.
       ^E	 Move cursor to end of line.
       M-[Y	 Move cursor to end of line.
       ^]char	 Move cursor forward to character char on current line.
       M-^]char	 Move cursor backward to character char on current line.
       ^X^X	 Interchange the cursor and mark.
       erase	 (User	defined erase character as defined by the stty(1) com‐
		 mand, usually ^H or #.)  Delete previous character.
       lnext	 (User defined	literal	 next  character  as  defined  by  the
		 stty(1)  command,  or	^V  if not defined.)  Removes the next
		 character's editing features (if any).
       ^D	 Delete current character.
       M-d	 Delete current word.
       M-^H	 (Meta-backspace) Delete previous word.
       M-h	 Delete previous word.
       M-^?	 (Meta-DEL) Delete previous word (if your interrupt  character
		 is ^?	(DEL, the default) then this command will not work).
       ^T	 Transpose  current  character	with  previous	character  and
		 advance the cursor in emacs  mode.   Transpose	 two  previous
		 characters in gmacs mode.
       ^C	 Capitalize current character.
       M-c	 Capitalize current word.
       M-l	 Change the current word to lower case.
       ^K	 Delete	 from  the cursor to the end of the line.  If preceded
		 by a numerical parameter whose value is less than the current
		 cursor	 position,  then  delete from given position up to the
		 cursor.  If preceded by a numerical parameter whose value  is
		 greater  than	the  current cursor position, then delete from
		 cursor up to given cursor position.
       ^W	 Kill from the cursor to the mark.
       M-p	 Push the region from the cursor to the mark on the stack.
       kill	 (User defined kill character as defined by the stty  command,
		 usually ^G or @.)  Kill the entire current line.  If two kill
		 characters are entered in  succession,	 all  kill  characters
		 from  then on cause a line feed (useful when using paper ter‐
		 minals).
       ^Y	 Restore last item removed from line. (Yank item back  to  the
		 line.)
       ^L	 Line feed and print current line.
       M-^L	 Clear the screen.
       ^@	 (Null character) Set mark.
       M-space	 (Meta space) Set mark.
       ^J	 (New line) Execute the current line.
       ^M	 (Return) Execute the current line.
       eof	 End-of-file  character,  normally ^D, is processed as an End-
		 of-file only if the current line is null.
       ^P	 Fetch previous command.  Each time ^P is entered the previous
		 command  back	in time is accessed.  Moves back one line when
		 not on the first line of a multi-line command.
       M-[A	 If the cursor is at the end of the line, it is equivalent  to
		 ^R with string set to the contents of the current line.  Oth‐
		 erwise, it is equivalent to ^P.
       M-<	 Fetch the least recent (oldest) history line.
       M->	 Fetch the most recent (youngest) history line.
       ^N	 Fetch next command line.  Each time ^N is  entered  the  next
		 command line forward in time is accessed.
       M-[B	 Equivalent to ^N.
       ^Rstring	 Reverse search history for a previous command line containing
		 string.  If a parameter of zero is given, the search is  for‐
		 ward.	 String is terminated by a `RETURN' or `NEW LINE'.  If
		 string is preceded by a ^, the matched line must  begin  with
		 string.   If  string  is  omitted, then the next command line
		 containing the most recent string is accessed.	 In this  case
		 a parameter of zero reverses the direction of the search.
       ^O	 Operate  -  Execute  the current line and fetch the next line
		 relative to current line from the history file.
       M-digits	 (Escape) Define numeric parameter, the digits are taken as  a
		 parameter  to	the  next command.  The commands that accept a
		 parameter are ^F, ^B, erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-.,
		 M-^], M-_, M-=, M-b, M-c, M-d, M-f, M-h, M-l and M-^H.
       M-letter	 Soft-key  -  Your  alias list is searched for an alias by the
		 name _letter and if an alias of this  name  is	 defined,  its
		 value	will  be inserted on the input queue.  The letter must
		 not be one of the above meta-functions.
       M-[letter Soft-key - Your alias list is searched for an	alias  by  the
		 name  __letter	 and  if an alias of this name is defined, its
		 value will be inserted on the input queue.  This can be  used
		 to program function keys on many terminals.
       M-.	 The  last  word  of  the  previous command is inserted on the
		 line.	If preceded by a numeric parameter, the value of  this
		 parameter  determines	which  word  to insert rather than the
		 last word.
       M-_	 Same as M-..
       M-*	 Attempt file name generation on the current word.  An	aster‐
		 isk is appended if the word doesn't match any file or contain
		 any special pattern characters.
       M-ESC	 Command or file name completion as described above.
       ^I tab	 Attempts command or file name completion as described	above.
		 If a partial completion occurs, repeating this will behave as
		 if M-= were entered.  If no match is found or	entered	 after
		 space, a tab is inserted.
       M-=	 If not preceded by a numeric parameter, it generates the list
		 of matching commands or file names as described above.	  Oth‐
		 erwise,  the  word  under  the cursor is replaced by the item
		 corresponding to the value of the numeric parameter from  the
		 most  recently generated command or file list.	 If the cursor
		 is not on a word, it is inserted instead.
       ^U	 Multiply parameter of next command by 4.
       \	 Escape next character.	 Editing characters, the user's erase,
		 kill  and  interrupt (normally ^?)  characters may be entered
		 in a command line or in a search string if preceded by	 a  \.
		 The \ removes the next character's editing features (if any).
       M-^V	 Display version of the shell.
       M-#	 If  the  line does not begin with a #, a # is inserted at the
		 beginning of the line and after each new-line, and  the  line
		 is entered.  This causes a comment to be inserted in the his‐
		 tory file.  If the line begins with a #, the # is deleted and
		 one # after each new-line is also deleted.

   Vi Editing Mode.
       There  are  two	typing modes.  Initially, when you enter a command you
       are in the input mode.  To edit, the user enters control mode by typing
       ESC (033) and moves the cursor to the point needing correction and then
       inserts or deletes characters or words as needed.   Most	 control  com‐
       mands accept an optional repeat count prior to the command.

       When  in	 vi  mode  on  most systems, canonical processing is initially
       enabled and the command will be echoed again if the speed is 1200  baud
       or greater and it contains any control characters or less than one sec‐
       ond has elapsed since the prompt was printed.  The ESC character termi‐
       nates  canonical	 processing  for  the remainder of the command and the
       user can then modify the command line.  This scheme has the  advantages
       of canonical processing with the type-ahead echoing of raw mode.

       If  the option viraw is also set, the terminal will always have canoni‐
       cal processing disabled.	 This mode is implicit for systems that do not
       support	two  alternate	end of line delimiters, and may be helpful for
       certain terminals.

	Input Edit Commands
	      By default the editor is in input mode.
	      erase	(User defined erase character as defined by  the  stty
			command, usually ^H or #.)  Delete previous character.
	      ^W	Delete	the  previous  blank  separated word.  On some
			systems the viraw option may be required for  this  to
			work.
	      eof	As the first character of the line causes the shell to
			terminate unless the ignoreeof option is set.	Other‐
			wise this character is ignored.
	      lnext	(User defined literal next character as defined by the
			stty(1) or ^V if not defined.)	Removes the next char‐
			acter's	 editing  features  (if any).  On some systems
			the viraw option may be required for this to work.
	      \		Escape the next erase or kill character.
	      ^I tab	Attempts command or file name completion as  described
			above and returns to input mode.  If a partial comple‐
			tion occurs, repeating this will behave as if  =  were
			entered	 from  control	mode.  If no match is found or
			entered after space, a tab is inserted.
	Motion Edit Commands
	      These commands will move the cursor.
	      [count]l	Cursor forward (right) one character.
	      [count][C Cursor forward (right) one character.
	      [count]w	Cursor forward one alpha-numeric word.
	      [count]W	Cursor to the beginning of the next word that  follows
			a blank.
	      [count]e	Cursor to end of word.
	      [count]E	Cursor to end of the current blank delimited word.
	      [count]h	Cursor backward (left) one character.
	      [count][D Cursor backward (left) one character.
	      [count]b	Cursor backward one word.
	      [count]B	Cursor to preceding blank separated word.
	      [count]⎪	Cursor to column count.
	      [count]fc Find the next character c in the current line.
	      [count]Fc Find the previous character c in the current line.
	      [count]tc Equivalent to f followed by h.
	      [count]Tc Equivalent to F followed by l.
	      [count];	Repeats	 count	times,	the last single character find
			command, f, F, t, or T.
	      [count],	Reverses the last single character find command	 count
			times.
	      0		Cursor to start of line.
	      ^		Cursor to start of line.
	      [H	Cursor to first non-blank character in line.
	      $		Cursor to end of line.
	      [Y	Cursor to end of line.
	      %		Moves  to balancing (, ), {, }, [, or ].  If cursor is
			not on one of the above characters, the	 remainder  of
			the  line  is searched for the first occurrence of one
			of the above characters first.
	Search Edit Commands
	      These commands access your command history.
	      [count]k	Fetch previous command.	 Each time k  is  entered  the
			previous command back in time is accessed.
	      [count]-	Equivalent to k.
	      [count][A If  cursor  is at the end of the line it is equivalent
			to / with string^set to the contents  of  the  current
			line.  Otherwise, it is equivalent to k.
	      [count]j	Fetch  next  command.  Each time j is entered the next
			command forward in time is accessed.
	      [count]+	Equivalent to j.
	      [count][B Equivalent to j.
	      [count]G	The command number count is fetched.  The  default  is
			the least recent history command.
	      /string	Search backward through history for a previous command
			containing string.  String is terminated by a `RETURN'
			or  `NEW LINE'.	  If  string  is  preceded by a ^, the
			matched line must begin with  string.	If  string  is
			null, the previous string will be used.
	      ?string	Same  as  /  except that search will be in the forward
			direction.
	      n		Search for next match of the last pattern to  /	 or  ?
			commands.
	      N		Search	for  next match of the last pattern to / or ?,
			but in reverse direction.
	Text Modification Edit Commands
	      These commands will modify the line.
	      a		Enter input mode and  enter  text  after  the  current
			character.
	      A		Append text to the end of the line.  Equivalent to $a.
	      [count]cmotion
	      c[count]motion
			Delete	current	 character  through the character that
			motion would move the cursor to and enter input	 mode.
			If  motion  is	c, the entire line will be deleted and
			input mode entered.
	      C		Delete the current character through the end  of  line
			and enter input mode.  Equivalent to c$.
	      S		Equivalent to cc.
	      [count]s	Replace characters under the cursor in input mode.
	      D		Delete	the current character through the end of line.
			Equivalent to d$.
	      [count]dmotion
	      d[count]motion
			Delete current character through  the  character  that
			motion	would  move  to.   If motion is d , the entire
			line will be deleted.
	      i		Enter input mode and insert text  before  the  current
			character.
	      I		Insert text before the beginning of the line.  Equiva‐
			lent to 0i.
	      [count]P	Place the previous text modification before  the  cur‐
			sor.
	      [count]p	Place the previous text modification after the cursor.
	      R		Enter  input mode and replace characters on the screen
			with characters you type overlay fashion.
	      [count]rc Replace the count character(s) starting at the current
			cursor position with c, and advance the cursor.
	      [count]x	Delete current character.
	      [count]X	Delete preceding character.
	      [count].	Repeat the previous text modification command.
	      [count]∼	Invert	the case of the count character(s) starting at
			the current cursor position and advance the cursor.
	      [count]_	Causes the count word of the previous  command	to  be
			appended  and  input  mode  entered.  The last word is
			used if count is omitted.
	      *		Causes an * to be appended to  the  current  word  and
			file name generation attempted.	 If no match is found,
			it rings the bell.  Otherwise, the word is replaced by
			the matching pattern and input mode is entered.
	      \		Command or file name completion as described above.
	Other Edit Commands
	      Miscellaneous commands.
	      [count]ymotion
	      y[count]motion
			Yank  current  character through character that motion
			would move the cursor to and puts them into the delete
			buffer.	 The text and cursor are unchanged.
	      yy	Yanks the entire line.
	      Y		Yanks  from  current position to end of line.  Equiva‐
			lent to y$.
	      u		Undo the last text modifying command.
	      U		Undo all the text modifying commands performed on  the
			line.
	      [count]v	Returns	 the  command hist -e ${VISUAL:-${EDITOR:-vi}}
			count in the input buffer.  If count is omitted,  then
			the current line is used.
	      ^L	Line  feed and print current line.  Has effect only in
			control mode.
	      ^J	(New line) Execute the	current	 line,	regardless  of
			mode.
	      ^M	(Return) Execute the current line, regardless of mode.
	      #		If  the	 first	character  of the command is a #, then
			this command deletes this # and each # that follows  a
			newline.   Otherwise, sends the line after inserting a
			# in front of each line in the	command.   Useful  for
			causing the current line to be inserted in the history
			as a comment  and  uncommenting	 previously  commented
			commands in the history file.
	      [count]=	If  count  is  not specified, it generates the list of
			matching commands or file names	 as  described	above.
			Otherwise,  the	 word under the the cursor is replaced
			by the count item from	the  most  recently  generated
			command or file list.  If the cursor is not on a word,
			it is inserted instead.
	      @letter	Your alias list is searched for an alias by  the  name
			_letter	 and  if an alias of this name is defined, its
			value will be inserted on the input queue for process‐
			ing.
	      ^V	Display version of the shell.

   Built-in Commands.
       The  following  simple-commands	are  executed  in  the	shell process.
       Input/Output redirection is permitted.  Unless otherwise indicated, the
       output  is written on file descriptor 1 and the exit status, when there
       is no syntax error, is zero.  Except for :, true, false, echo,  newgrp,
       and  login, all built-in commands accept -- to indicate end of options.
       They also interpret the option --man as a request to  display  the  man
       page onto standard error and -?	as a help request which prints a usage
       message on standard error.  Commands that are preceded by one or two  †
       symbols	are special built-in commands and are treated specially in the
       following ways:
       1.     Variable assignment lists preceding the command remain in effect
	      when the command completes.
       2.     I/O redirections are processed after variable assignments.
       3.     Errors cause a script that contains them to abort.
       4.     They are not valid function names.
       5.     Words  following a command preceded by †† that are in the format
	      of a variable assignment are expanded with the same rules	 as  a
	      variable assignment.  This means that tilde substitution is per‐
	      formed after the = sign and field splitting and file name gener‐
	      ation  are  not  performed.  These are called declaration built-
	      ins.

       † : [ arg ... ]
	      The command only expands parameters.

       † . name [ arg ... ]
	      If name is a function defined with the  function	name  reserved
	      word syntax, the function is executed in the current environment
	      (as if it had been defined with the name()  syntax.)   Otherwise
	      if  name	refers to a file, the file is read in its entirety and
	      the commands are executed in the current shell environment.  The
	      search path specified by PATH is used to find the directory con‐
	      taining the file.	 If any arguments arg are given,  they	become
	      the  positional  parameters  while processing the .  command and
	      the original positional parameters are restored upon completion.
	      Otherwise	 the  positional  parameters  are unchanged.  The exit
	      status is the exit status of the last command executed.

       †† alias [ -ptx ]  [ name[ =value  ] ] ...
	      alias with no arguments prints the list of aliases in  the  form
	      name=value  on  standard	output.	 The -p option causes the word
	      alias to be inserted before each one.  When one  or  more	 argu‐
	      ments  are  given, an alias is defined for each name whose value
	      is given.	 A trailing space in value causes the next word to  be
	      checked  for alias substitution.	The obsolete -t option is used
	      to set and list tracked aliases.	The value of a	tracked	 alias
	      is the full pathname corresponding to the given name.  The value
	      becomes undefined when the value of PATH is reset but the	 alias
	      remains  tracked.	  Without  the -t option, for each name in the
	      argument list for which no value is given, the name and value of
	      the  alias  is  printed.	 The obsolete -x option has no effect.
	      The exit status is non-zero if a name is given,  but  no	value,
	      and no alias has been defined for the name.

       bg [ job... ]
	      This  command is only on systems that support job control.  Puts
	      each specified job into the background.  The current job is  put
	      in  the  background  if  job  is	not specified.	See Jobs for a
	      description of the format of job.

       † break [ n ]
	      Exit from the enclosing for, while, until, or  select  loop,  if
	      any.  If n is specified, then break n levels.

       builtin [ -ds ] [ -f file ] [ name ... ]
	      If  name	is  not	 specified, and no -f option is specified, the
	      built-ins are printed on standard output.	 The -s option	prints
	      only the special built-ins.  Otherwise, each name represents the
	      pathname whose basename is the name of the built-in.  The	 entry
	      point function name is determined by prepending b_ to the built-
	      in name.	The ISO C/C++ prototype is b_mycommand(int argc,  char
	      *argv[],	void *context) for the builtin command mycommand where
	      argv is array an of argc elements and  context  is  an  optional
	      pointer to a Shell_t structure as described in <ast/shell.h>.
	      Special built-ins cannot be bound to a pathname or deleted.  The
	      -d option deletes each of the given built-ins.  On systems  that
	      support  dynamic	loading,  the -f option names a shared library
	      containing the code for built-ins.  The  shared  library	prefix
	      and/or suffix, which depend on the system, can be omitted.  Once
	      a library is loaded, its symbols become available for subsequent
	      invocations  of  builtin.	  Multiple  libraries can be specified
	      with separate invocations of the builtin command.	 Libraries are
	      searched in the reverse order in which they are specified.  When
	      a library is loaded, it looks for	 a  function  in  the  library
	      whose name is lib_init() and invokes this function with an argu‐
	      ment of 0.

       cd [ -LP ] [ arg ]
       cd [ -LP ] old new
	      This command can be in either of two forms.  In the  first  form
	      it changes the current directory to arg.	If arg is - the direc‐
	      tory is changed to the previous directory.  The  shell  variable
	      HOME is the default arg.	The variable PWD is set to the current
	      directory.  The shell variable CDPATH defines  the  search  path
	      for  the	directory containing arg.  Alternative directory names
	      are separated by a colon (:).  The default path is <null> (spec‐
	      ifying  the current directory).  Note that the current directory
	      is specified by a null path name, which can  appear  immediately
	      after  the  equal	 sign or between the colon delimiters anywhere
	      else in the path list.  If arg begins with a / then  the	search
	      path  is	not  used.   Otherwise,	 each directory in the path is
	      searched for arg.
	      The second form of cd substitutes the string new for the	string
	      old  in  the current directory name, PWD, and tries to change to
	      this new directory.
	      By default, symbolic link names are treated literally when find‐
	      ing  the	directory  name.  This is equivalent to the -L option.
	      The -P option causes symbolic links to be resolved  when	deter‐
	      mining the directory.  The last instance of -L or -P on the com‐
	      mand line determines which method is used.
	      The cd command may not be executed by rksh.  rksh93.

       command [ -pvxV ] name [ arg ... ]
	      Without the -v or -V options, command  executes  name  with  the
	      arguments	 given by arg.	The -p option causes a default path to
	      be searched rather than the one defined by the  value  of	 PATH.
	      Functions	 will not be searched for when finding name.  In addi‐
	      tion, if name refers to a special built-in, none of the  special
	      properties  associated with the leading daggers will be honored.
	      (For example, the predefined alias redirect=′command exec′  pre‐
	      vents  a	script from terminating when an invalid redirection is
	      given.)  With the -x option, if command execution	 would	result
	      in  a failure because there are too many arguments, errno E2BIG,
	      the shell will invoke command name multiple times with a	subset
	      of the arguments on each invocation.  Arguments that occur prior
	      to the first word that expands to multiple arguments  and	 after
	      the  last word that expands to multiple arguments will be passed
	      on each invocation.  The exit status will be the maximum invoca‐
	      tion  exit status.  With the -v option, command is equivalent to
	      the built-in whence command  described  below.   The  -V	option
	      causes command to act like whence -v.

       † continue [ n ]
	      Resume the next iteration of the enclosing for, while, until, or
	      select loop.  If n is specified, then resume at the n-th enclos‐
	      ing loop.

       disown [ job... ]
	      Causes  the shell not to send a HUP signal to each given job, or
	      all active jobs if job is omitted, when  a  login	 shell	termi‐
	      nates.

       echo [ arg ... ]
	      When  the	 first	arg  does  not begin with a -, and none of the
	      arguments contain a \, then echo prints each  of	its  arguments
	      separated	 by  a space and terminated by a new-line.  Otherwise,
	      the behavior of echo is system dependent	and  print  or	printf
	      described	 below	should	be  used.   See	 echo(1) for usage and
	      description.

       †† enum [ -i  ] type[=(value ...) ]
	      Creates a declaration command named type that is an integer type
	      that  allows  one	 of the specified values as enumeration names.
	      If =(value ...) is omitted, then type must be an	indexed	 array
	      variable	with  at  least	 two elements and the values are taken
	      from this array variable.	 If -i is  specified  the  values  are
	      case insensitive.

       † eval [ arg ... ]
	      The  arguments  are read as input to the shell and the resulting
	      command(s) executed.

       † exec [ -c ] [ -a name ] [ arg ... ]
	      If arg is given, the command specified by the arguments is  exe‐
	      cuted  in	 place	of  this shell without creating a new process.
	      The -c option causes the environment to be cleared before apply‐
	      ing  variable  assignments  associated with the exec invocation.
	      The -a option causes name rather than the first arg,  to	become
	      argv[0]  for the new process.  Input/output arguments may appear
	      and affect the current process.  If arg is not given, the effect
	      of  this	command is to modify file descriptors as prescribed by
	      the input/output redirection  list.   In	this  case,  any  file
	      descriptor  numbers  greater  than  2  that are opened with this
	      mechanism are closed when invoking another program.

       † exit [ n ]
	      Causes the shell to exit with the exit status  specified	by  n.
	      The  value will be the least significant 8 bits of the specified
	      status.  If n is omitted, then the exit status is	 that  of  the
	      last command executed.  An end-of-file will also cause the shell
	      to exit except for a shell which has the ignoreeof  option  (see
	      set below) turned on.

       †† export [ -p ] [ name[=value] ] ...
	      If name is not given, the names and values of each variable with
	      the export attribute are printed with the	 values	 quoted	 in  a
	      manner  that  allows them to be re-input.	 The export command is
	      the same as typeset -x except that if you use  export  within  a
	      function,	 no  local  variable is created.  The -p option causes
	      the word export to be inserted before each one.  Otherwise,  the
	      given  names  are marked for automatic export to the environment
	      of subsequently-executed commands.

       false  Does nothing, and exits 1. Used with until for infinite loops.

       fg [ job... ]
	      This command is only on systems that support job control.	  Each
	      job specified is brought to the foreground and waited for in the
	      specified order.	Otherwise, the current job is brought into the
	      foreground.  See Jobs for a description of the format of job.

       getconf [ name [ pathname ] ]
	      Prints the current value of the configuration parameter given by
	      name.  The configuration parameters  are	defined	 by  the  IEEE
	      POSIX  1003.1 and IEEE POSIX 1003.2 standards.  (See pathconf(2)
	      and sysconf(2).)	The pathname argument is required for  parame‐
	      ters whose value depends on the location in the file system.  If
	      no arguments are given, getconf prints the names and  values  of
	      the  current  configuration  parameters.	The pathname / is used
	      for each of the parameters that requires pathname.

       getopts [  -a name ] optstring vname [ arg ... ]
	      Checks arg for legal options.  If arg is omitted, the positional
	      parameters are used.  An option argument begins with a + or a -.
	      An option not beginning with + or - or the argument -- ends  the
	      options.	Options beginning with + are only recognized when opt‐
	      string begins with a +.  optstring  contains  the	 letters  that
	      getopts recognizes.  If a letter is followed by a :, that option
	      is expected to have an argument.	The options can	 be  separated
	      from  the	 argument by blanks.  The option -?  causes getopts to
	      generate a usage message on standard error.  The -a argument can
	      be  used to specify the name to use for the usage message, which
	      defaults to $0.
	      getopts places the next option letter it finds  inside  variable
	      vname  each  time	 it  is	 invoked.   The	 option letter will be
	      prepended with a + when arg begins with a +.  The index  of  the
	      next arg is stored in OPTIND.  The option argument, if any, gets
	      stored in OPTARG.
	      A leading : in optstring causes getopts to store the  letter  of
	      an  invalid  option  in  OPTARG,	and  to set vname to ?	for an
	      unknown option and to : when a required option argument is miss‐
	      ing.  Otherwise, getopts prints an error message.	 The exit sta‐
	      tus is non-zero when there are no more options.
	      There is no way to specify any of the options :, +, -, ?, [, and
	      ].  The option # can only be specified as the first option.

       hist [ -e ename	] [ -nlr ] [ first [ last ] ]
       hist -s	[ old=new ] [ command ]
	      In  the  first  form,  a range of commands from first to last is
	      selected from the last HISTSIZE commands that were typed at  the
	      terminal.	  The  arguments  first and last may be specified as a
	      number or as a string.  A string is  used	 to  locate  the  most
	      recent  command starting with the given string.  A negative num‐
	      ber is used as an offset to the current command number.  If  the
	      -l  option is selected, the commands are listed on standard out‐
	      put.  Otherwise, the editor program ename is invoked on  a  file
	      containing  these	 keyboard commands.  If ename is not supplied,
	      then the value of the variable HISTEDIT is used.	If HISTEDIT is
	      not  set,	 then  FCEDIT (default /bin/ed) is used as the editor.
	      When editing is complete, the edited command(s) is  executed  if
	      the  changes have been saved.  If last is not specified, then it
	      will be set to first.  If first is not specified, the default is
	      the  previous  command  for  editing  and	 -16 for listing.  The
	      option -r reverses the order of the commands and the  option  -n
	      suppresses  command  numbers  when listing.  In the second form,
	      command is interpreted as first described above and defaults  to
	      the  last	 command  executed.  The resulting command is executed
	      after the optional substitution old=new is performed.

       jobs [ -lnp ] [ job ... ]
	      Lists information about each given job; or all  active  jobs  if
	      job  is omitted.	The -l option lists process ids in addition to
	      the normal information.  The -n option only displays  jobs  that
	      have  stopped  or	 exited	 since	last  notified.	 The -p option
	      causes only the process group to be  listed.   See  Jobs	for  a
	      description of the format of job.

       kill [ -s signame ] job ...
       kill [ -n signum ] job ...
       kill -l [ sig ... ]
	      Sends either the TERM (terminate) signal or the specified signal
	      to the specified jobs or processes.  Signals are either given by
	      number  with  the	 -n  option  or by name with the -s option (as
	      given in <signal.h>, stripped of the  prefix  ``SIG''  with  the
	      exception	 that SIGCLD is named CHLD).  For backward compatibil‐
	      ity, the n and s can be omitted and the number  or  name	placed
	      immediately after the -.	If the signal being sent is TERM (ter‐
	      minate) or HUP (hangup), then the job or process will be sent  a
	      CONT  (continue)	signal if it is stopped.  The argument job can
	      be the process id of a process that is not a member  of  one  of
	      the  active  jobs.   See Jobs for a description of the format of
	      job.  In the third form, kill -l, if sig is not  specified,  the
	      signal  names  are  listed.   Otherwise,	for each sig that is a
	      name, the corresponding signal number is listed.	For  each  sig
	      that  is	a  number,  the signal name corresponding to the least
	      significant 8 bits of sig is listed.

       let arg ...
	      Each arg is a separate arithmetic expression  to	be  evaluated.
	      See Arithmetic Evaluation above, for a description of arithmetic
	      expression evaluation.
	      The exit status is 0 if the value of the last expression is non-
	      zero, and 1 otherwise.

       † newgrp [ arg ... ]
	      Equivalent to exec /bin/newgrp arg ....

       print [ -CRenprsv ] [ -u unit] [ -f format ] [ arg ... ]
	      With  no	options or with option - or --, each arg is printed on
	      standard output.	The -f	option	causes	the  arguments	to  be
	      printed  as  described  by printf.  In this case, any e, n, r, R
	      options are ignored.  Otherwise, unless the -C, -R,  -r,	or  -v
	      are specified, the following escape conventions will be applied:
	      \a     The alert character (ascii 07).
	      \b     The backspace character (ascii 010).
	      \c     Causes print to end without processing more arguments and
		     not adding a new-line.
	      \f     The formfeed character (ascii 014).
	      \n     The new-line character (ascii 012).
	      \r     The carriage return character (ascii 015).
	      \t     The tab character (ascii 011).
	      \v     The vertical tab character (ascii 013).
	      \E     The escape character (ascii 033).
	      \\     The backslash character \.
	      \0x    The character defined by  the  1,	2,  or	3-digit	 octal
		     string given by x.

	      The  -R  option  will print all subsequent arguments and options
	      other than -n.  The -e causes the above escape conventions to be
	      applied.	 This is the default behavior.	It reverses the effect
	      of an earlier -r.	 The -p option	causes	the  arguments	to  be
	      written  onto the pipe of the process spawned with ⎪& instead of
	      standard output.	The -v option treats each arg  as  a  variable
	      name  and	 writes	 the  value  in	 the printf %B format.	The -C
	      option treats each arg as a variable name and writes  the	 value
	      in the printf %#B format.	 The -s option causes the arguments to
	      be written onto the history file	instead	 of  standard  output.
	      The -u option can be used to specify a one digit file descriptor
	      unit number unit on  which  the  output  will  be	 placed.   The
	      default is 1.  If the option -n is used, no new-line is added to
	      the output.

       printf format [ arg ... ]
	      The arguments arg are printed on standard output	in  accordance
	      with  the	 ANSI-C	 formatting  rules  associated with the format
	      string format.  If the number of arguments exceeds the number of
	      format  specifications,  the  format  string is reused to format
	      remaining arguments.  The following extensions can also be used:
	      %b     A %b format can be used instead of	 %s  to	 cause	escape
		     sequences	in  the	 corresponding	arg  to be expanded as
		     described in print.
	      %B     A %B option causes each of the arguments to be treated as
		     variable  names  and the binary value of variable will be
		     printed.  The alternate flag # causes a compound variable
		     to	 be  output on a single line.  This is most useful for
		     compound variables and variables whose attribute is -b.
	      %H     A %H format can be used instead of %s to cause characters
		     in	 arg  that are special in HTML and XML to be output as
		     their entity name.
	      %P     A %P format can be used instead of %s to cause arg to  be
		     interpreted  as  an  extended  regular  expression and be
		     printed as a shell pattern.
	      The format modifier
		     L can be used with the %c and %s formats to treat	preci‐
		     sion as character width instead of byte count.
	      The format modifier
		     ,	can  be used with the %d and %f formats to treat sepa‐
		     rate groups of digits with the grouping  delimiter	 which
		     is %d in the C locale.
	      %R     A	%R format can be used instead of %s to cause arg to be
		     interpreted as a shell pattern and to be  printed	as  an
		     extended regular expression.
	      %q     A	%q  format  can	 be  used  instead  of %s to cause the
		     resulting string to be quoted in a	 manner	 than  can  be
		     reinput to the shell.
	      %(date-format)T
		     A	%(date-format)T format can be use to treat an argument
		     as a date/time string and to format the date/time accord‐
		     ing  to  the  date-format as defined for the date(1) com‐
		     mand.
	      %Z     A %Z format will output a byte whose value is 0.
	      %d     The precision field of the %d format can be followed by a
		     .	and the output base.  In this case, the # flag charac‐
		     ter causes base# to be prepended.
	      #	     The # flag when used with the d specifier without an out‐
		     put  base, causes the output to be displayed in thousands
		     units with one of the suffixes k M G T P  E  to  indicate
		     the  unit.	  The  #  flag	when used with the i specifier
		     causes the output to be displayed in 1024 with one of the
		     suffixes Ki Mi Gi Ti Pi Ei to indicate the unit.
	      =	     The = flag has been added to center the output within the
		     specified field width.

       pwd [ -LP ]
	      Outputs the value of the	current	 working  directory.   The  -L
	      option is the default; it prints the logical name of the current
	      directory.  If the -P option is given, all  symbolic  links  are
	      resolved	from  the  name.  The last instance of -L or -P on the
	      command line determines which method is used.

       read [ -ACprsv ] [ -d delim] [ -n n] [ [ -N n] [ [  -t  timeout]	 [  -u
       unit] [ vname?prompt ] [ vname ... ]
	      The  shell  input	 mechanism.  One line is read and is broken up
	      into fields using the characters	in  IFS	 as  separators.   The
	      escape  character,  \, is used to remove any special meaning for
	      the next character and for line  continuation.   The  -d	option
	      causes  the  read	 to  continue  to the first character of delim
	      rather than new-line.  The -n option causes at most n  bytes  to
	      read rather a full line but will return when reading from a slow
	      device as soon as any characters have been read.	The -N	option
	      causes  exactly  n  to  be  read	unless an end-of-file has been
	      encountered or the read times out because of the -t option.   In
	      raw  mode,  -r,  the  \ character is not treated specially.  The
	      first field is assigned to the first vname, the second field  to
	      the  second  vname,  etc.,  with leftover fields assigned to the
	      last vname.  When vname has the binary attribute and -n or -N is
	      specified,  the bytes that are read are stored directly into the
	      variable.	 If the -v is specified, then the value of  the	 first
	      vname will be used as a default value when reading from a termi‐
	      nal device.  The -A option causes the variable vname to be unset
	      and  each field that is read to be stored in successive elements
	      of the indexed array vname.  The -C option causes	 the  variable
	      vname to be read as a compound variable.	Blanks will be ignored
	      when finding the beginning  open	parenthesis.   The  -p	option
	      causes  the  input  line	to  be	taken from the input pipe of a
	      process spawned by the shell using ⎪&.   If  the	-s  option  is
	      present,	the  input  will  be saved as a command in the history
	      file.  The option -u can be used to specify  a  one  digit  file
	      descriptor  unit	unit to read from.  The file descriptor can be
	      opened with the exec  special  built-in  command.	  The  default
	      value  of unit n is 0.  The option -t is used to specify a time‐
	      out in seconds when reading from a terminal or pipe.   If	 vname
	      is omitted, then REPLY is used as the default vname.  An end-of-
	      file with the -p option causes cleanup for this process so  that
	      another can be spawned.  If the first argument contains a ?, the
	      remainder of this word is used as a  prompt  on  standard	 error
	      when  the	 shell is interactive.	The exit status is 0 unless an
	      end-of-file is encountered or read has timed out.

       †† readonly [ -p ] [ vname[=value] ] ...
	      If vname is not given, the names and  values  of	each  variable
	      with the readonly attribute is printed with the values quoted in
	      a manner that allows them to  be	re-inputted.   The  -p	option
	      causes the word readonly to be inserted before each one.	Other‐
	      wise, the given vnames are marked readonly and these names  can‐
	      not  be changed by subsequent assignment.	 When defining a type,
	      if the value of a readonly sub-variable is not defined the value
	      is required when creating each instance.

       † return [ n ]
	      Causes  a	 shell function or .  script to return to the invoking
	      script with the exit status specified by n.  The value  will  be
	      the  least  significant 8 bits of the specified status.  If n is
	      omitted, then the return status is that of the last command exe‐
	      cuted.   If  return  is  invoked	while not in a function or a .
	      script, then it behaves the same as exit.

       † set [ ±BCGabefhkmnoprstuvx ] [ ±o [ option ] ] ... [ ±A  vname	 ]   [
       arg ... ]
	      The options for this command have meaning as follows:
	      -A      Array  assignment.   Unset the variable vname and assign
		      values sequentially from the arg list.  If +A  is	 used,
		      the variable vname is not unset first.
	      -B      Enable  brace  pattern  field  generation.   This is the
		      default behavior.
	      -B      Enable brace group expansion.  On by default.
	      -C      Prevents redirection > from truncating  existing	files.
		      Files  that are created are opened with the O_EXCL mode.
		      Requires >⎪ to truncate a file when turned on.
	      -G      Causes the pattern ∗∗ by itself to match files and  zero
		      or  more	directories  and sub-directories when used for
		      file name generation.  If followed by a / only  directo‐
		      ries and sub-directories are matched.
	      -a      All  subsequent variables that are defined are automati‐
		      cally exported.
	      -b      Prints job completion messages as soon as	 a  background
		      job  changes  state  rather  than	 waiting  for the next
		      prompt.
	      -e      Unless contained in a ⎪⎪ or && command, or  the  command
		      following	 an  if while or until command or in the pipe‐
		      line following !, if a command has a non-zero exit  sta‐
		      tus,  execute the ERR trap, if set, and exit.  This mode
		      is disabled while reading profiles.
	      -f      Disables file name generation.
	      -h      Each command becomes a tracked alias when first  encoun‐
		      tered.
	      -k      (Obsolete). All variable assignment arguments are placed
		      in the environment for a command, not  just  those  that
		      precede the command name.
	      -m      Background jobs will run in a separate process group and
		      a line will print upon completion.  The exit  status  of
		      background jobs is reported in a completion message.  On
		      systems with job control, this option is turned on auto‐
		      matically for interactive shells.
	      -n      Read  commands  and check them for syntax errors, but do
		      not execute them.	 Ignored for interactive shells.
	      -o      The following argument  can  be  one  of	the  following
		      option names:
		      allexport
			      Same as -a.
		      errexit Same as -e.
		      bgnice  All background jobs are run at a lower priority.
			      This is the default mode.
		      braceexpand
			      Same as -B.
		      emacs   Puts you in an emacs style  in-line  editor  for
			      command entry.
		      globstar
			      Same as -G.
		      gmacs   Puts  you	 in  a	gmacs style in-line editor for
			      command entry.
		      ignoreeof
			      The shell will not  exit	on  end-of-file.   The
			      command exit must be used.
		      keyword Same as -k.
		      markdirs
			      All  directory  names  resulting	from file name
			      generation have a trailing / appended.
		      monitor Same as -m.
		      multiline
			      The built-in editors will use multiple lines  on
			      the  screen  for	lines that are longer than the
			      width of the screen.  This may not work for  all
			      terminals.
		      noclobber
			      Same as -C.
		      noexec  Same as -n.
		      noglob  Same as -f.
		      nolog   Do  not save function definitions in the history
			      file.
		      notify  Same as -b.
		      nounset Same as -u.
		      pipefail
			      A pipeline will not complete  until  all	compo‐
			      nents  of	 the  pipeline have completed, and the
			      return value will be the value of the last  non-
			      zero  command  to fail or zero if no command has
			      failed.
		      showme  When enabled, simple commands or pipelines  pre‐
			      ceded by a semicolon (;) will be displayed as if
			      the xtrace option were enabled but will  not  be
			      executed.	  Otherwise,  the  leading  ;  will be
			      ignored.
		      privileged
			      Same as -p.
		      verbose Same as -v.
		      trackall
			      Same as -h.
		      vi      Puts you in insert mode of a  vi	style  in-line
			      editor  until  you hit the escape character 033.
			      This puts you in control mode.  A	 return	 sends
			      the line.
		      viraw   Each character is processed as it is typed in vi
			      mode.
		      xtrace  Same as -x.
		      If no option name is supplied, then the  current	option
		      settings are printed.
	      -p      Disables	processing of the $HOME/.profile file and uses
		      the file /etc/suid_profile  instead  of  the  ENV	 file.
		      This  mode is on whenever the effective uid (gid) is not
		      equal to the real uid (gid).  Turning  this  off	causes
		      the  effective uid and gid to be set to the real uid and
		      gid.
	      -r      Enables the restricted shell.   This  option  cannot  be
		      unset once set.
	      -s      Sort the positional parameters lexicographically.
	      -t      (Obsolete).   Exit  after reading and executing one com‐
		      mand.
	      -u      Treat unset parameters as an error when substituting.
	      -v      Print shell input lines as they are read.
	      -x      Print commands and their arguments as they are executed.
	      --      Do not change any of the options; useful in  setting  $1
		      to  a  value  beginning  with -.	If no arguments follow
		      this option then the positional parameters are unset.

	      As an obsolete feature, if the first arg is - then the -x and -v
	      options  are turned off and the next arg is treated as the first
	      argument.	 Using + rather than -	causes	these  options	to  be
	      turned  off.   These options can also be used upon invocation of
	      the shell.  The current set of  options  may  be	found  in  $-.
	      Unless  -A  is specified, the remaining arguments are positional
	      parameters and are assigned, in order, to	 $1  $2	 ....	If  no
	      arguments	 are given, then the names and values of all variables
	      are printed on the standard output.

       † shift [ n ]
	      The positional parameters from $n+1 ...  are renamed  $1	...  ,
	      default  n  is 1.	 The parameter n can be any arithmetic expres‐
	      sion that evaluates to a non-negative number less than or	 equal
	      to $#.

       sleep seconds
	      Suspends	execution  for	the number of decimal seconds or frac‐
	      tions of a second given by seconds.

       † trap [ -p ] [ action ] [ sig ] ...
	      The -p option causes the trap action associated with  each  trap
	      as  specified  by	 the  arguments to be printed with appropriate
	      quoting.	Otherwise, action will be processed as if it  were  an
	      argument	to  eval  when the shell receives signal(s) sig.  Each
	      sig can be given as a number or as the name of the signal.  Trap
	      commands are executed in order of signal number.	Any attempt to
	      set a trap on a signal that was ignored on entry to the  current
	      shell is ineffective.  If action is omitted and the first sig is
	      a number, or if action is -, then the trap(s) for each  sig  are
	      reset  to	 their	original values.  If action is the null string
	      then this signal is ignored by the shell and by the commands  it
	      invokes.	 If sig is ERR then action will be executed whenever a
	      command has a non-zero exit status.  If sig is DEBUG then action
	      will  be executed before each command.  The variable .sh.command
	      will contain the contents	 of  the  current  command  line  when
	      action is running.  If the exit status of the trap is 2 the com‐
	      mand will not be executed.  If the exit status of	 the  trap  is
	      255  and	inside a function or a dot script, the function or dot
	      script will return.  If sig is 0 or EXIT and the trap  statement
	      is executed inside the body of a function defined with the func‐
	      tion name syntax, then the command action is executed after  the
	      function	completes.  If sig is 0 or EXIT for a trap set outside
	      any function then the command action is executed	on  exit  from
	      the  shell.  If sig is KEYBD, then action will be executed when‐
	      ever a key is read while in emacs, gmacs, or vi mode.  The  trap
	      command  with  no arguments prints a list of commands associated
	      with each signal number.

       An exit or return without an argument in a trap	action	will  preserve
       the exit status of the command that invoked the trap.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       true   Does nothing, and exits 0. Used with while for infinite loops.

       ††  typeset [ ±ACHSflbnprtux ] [ ±EFLRXZi[n] ]	[ +-M  [ mapname ] ] [
       -T  [ tname=(assign_list) ] ] [ -h str ] [ -a [type] ] [ vname[=value ]
	] ...
	      Sets  attributes	and  values for shell variables and functions.
	      When invoked inside a function defined with  the	function  name
	      syntax, a new instance of the variable vname is created, and the
	      variable's value and type are restored when  the	function  com‐
	      pletes.  The following list of attributes may be specified:
	      -A     Declares  vname  to  be an associative array.  Subscripts
		     are strings rather than arithmetic expressions.
	      -C     causes each vname to be a compound variable.  value names
		     a	compound variable it is copied into vname.  Otherwise,
		     it unsets each vname.
	      -a     Declares vname to be an indexed array.  If type is speci‐
		     fied,  it must be the name of an enumeration type created
		     with the enum command and it allows enumeration constants
		     to be used as subscripts.
	      -E     Declares  vname  to  be a double precision floating point
		     number.  If n is non-zero, it defines the number of  sig‐
		     nificant  figures	that  are  used	 when expanding vname.
		     Otherwise, ten significant figures will be used.
	      -F     Declares vname to be a double  precision  floating	 point
		     number.   If  n  is  non-zero,  it	 defines the number of
		     places after the decimal point that are used when expand‐
		     ing  vname.  Otherwise ten places after the decimal point
		     will be used.
	      -H     This option provides UNIX to host-name  file  mapping  on
		     non-UNIX machines.
	      -L     Left  justify and remove leading blanks from value.  If n
		     is non-zero, it defines the width of the field, otherwise
		     it	 is  determined	 by  the  width	 of the value of first
		     assignment.  When the variable  is	 assigned  to,	it  is
		     filled  on	 the right with blanks or truncated, if neces‐
		     sary, to fit into the field.  The	-R  option  is	turned
		     off.
	      -M     Use  the character mapping mapping defined by wctrans(3).
		     such as tolower and toupper when  assigning  a  value  to
		     each  of  the specified operands.	When mapping is speci‐
		     fied and there are not operands, all variables  that  use
		     this  mapping  are written to standard output.  When map‐
		     ping is omitted and there are  no	operands,  all	mapped
		     variables are written to standard output.
	      -R     Right justify and fill with leading blanks.  If n is non-
		     zero, it defines the width of the field, otherwise it  is
		     determined by the width of the value of first assignment.
		     The field is left filled with blanks  or  truncated  from
		     the  end if the variable is reassigned.  The -L option is
		     turned off.
	      -S     When used within the assign_list of a type definition, it
		     causes  the  specified  sub-variable  to be shared by all
		     instances of the  type.   When  used  inside  a  function
		     defined  with  the	 function reserved word, the specified
		     variables will have function  static  scope.   Otherwise,
		     the  variable is unset prior to processing the assignment
		     list.
	      -T     If followed by tname, it creates a type  named  by	 tname
		     using the compound assignment assign_list to tname.  Oth‐
		     erwise, it writes all the type  definitions  to  standard
		     output.
	      -X     Declares  vname  to  be a double precision floating point
		     number and expands using the %a format of ISO-C99.	 If  n
		     is	 non-zero,  it	defines the number of hex digits after
		     the radix point that is used when expanding  vname.   The
		     default is 10.
	      -Z     Right  justify  and  fill with leading zeros if the first
		     non-blank character is a digit and the -L option has  not
		     been  set.	 Remove leading zeros if the -L option is also
		     set.  If n is non-zero,  it  defines  the	width  of  the
		     field,  otherwise	it  is	determined by the width of the
		     value of first assignment.
	      -f     The names refer to function names	rather	than  variable
		     names.   No  assignments  can  be made and the only other
		     valid options are -S, -t, -u and -x.  The -S can be  used
		     with  discipline  functions defined in a type to indicate
		     that the function is static.  For a static function,  the
		     same method will be used by all instances of that type no
		     matter which instance references it.  In additon, it  can
		     only  use value of variables from the original type defi‐
		     nition.  These discipline functions cannot	 be  redefined
		     in	 any  type instance.  The -t option turns on execution
		     tracing for this function.	 The  -u  option  causes  this
		     function to be marked undefined.  The FPATH variable will
		     be searched to find  the  function	 definition  when  the
		     function  is  referenced.	If no options other than -f is
		     specified, then the function definition will be displayed
		     on standard output.  If +f is specified, then a line con‐
		     taining the function name followed	 by  a	shell  comment
		     containing	 the  line  number  and	 path name of the file
		     where this function was defined, if any, is displayed.
	      -b     The variable can hold any number of bytes of  data.   The
		     data  can be text or binary.  The value is represented by
		     the base64 encoding of the data.  If -Z  is  also	speci‐
		     fied, the size in bytes of the data in the buffer will be
		     determined by the size associated with the	 -Z.   If  the
		     base64  string  assigned results in more data, it will be
		     truncated.	 Otherwise, it will be filled with bytes whose
		     value  is zero.  The printf format %B can be used to out‐
		     put the actual data in this buffer instead of the	base64
		     encoding of the data.
	      -h     Used within type definitions to add information when gen‐
		     erating information about the  sub-variable  on  the  man
		     page.   It is ignored when used outside of a type defini‐
		     tion.  When used with -f the  information	is  associated
		     with the corresponding discipline function.
	      -i     Declares  vname  to be represented internally as integer.
		     The right hand side of an assignment is evaluated	as  an
		     arithmetic expression when assigning to an integer.  If n
		     is non-zero, it defines the output arithmetic base,  oth‐
		     erwise the output base will be ten.
	      -l     Used with -i, -E or -F, to indicate long integer, or long
		     float.  Otherwise, all  upper-case	 characters  are  con‐
		     verted  to	 lower-case.   The  upper-case	option, -u, is
		     turned off.  Equivalent to -M tolower .
	      -n     Declares vname to be a reference to  the  variable	 whose
		     name  is defined by the value of variable vname.  This is
		     usually used to reference a variable  inside  a  function
		     whose name has been passed as an argument.
	      -p     The  name, attributes and values for the given vnames are
		     written on standard output in a form that can be used  as
		     shell input.  If +p is specified, then the values are not
		     displayed.
	      -r     The given vnames are marked readonly and these names can‐
		     not be changed by subsequent assignment.
	      -t     Tags  the variables.  Tags are user definable and have no
		     special meaning to the shell.
	      -u     When given along with  -i,	 specifies  unsigned  integer.
		     Otherwise,	 all  lower-case  characters  are converted to
		     upper-case.  The lower-case option, -l,  is  turned  off.
		     Equivalent to -M toupper .
	      -x     The  given	 vnames are marked for automatic export to the
		     environment of subsequently-executed commands.  Variables
		     whose names contain a .  cannot be exported.

	      The  -i  attribute cannot be specified along with -R, -L, -Z, or
	      -f.

	      Using + rather than - causes these options to be turned off.  If
	      no  vname	 arguments are given, a list of vnames (and optionally
	      the values) of the variables is printed.	(Using + rather than -
	      keeps  the  values  from	being  printed.)  The -p option causes
	      typeset followed by the option letters to be printed before each
	      name  rather than the names of the options.  If any option other
	      than -p is given, only those variables which  have  all  of  the
	      given options are printed.  Otherwise, the vnames and attributes
	      of all variables that have attributes are printed.

       ulimit [ -HSacdfmnpstv ] [ limit ]
	      Set or display a resource limit.	The available resource	limits
	      are  listed  below.   Many systems do not support one or more of
	      these limits.  The limit for a specified resource	 is  set  when
	      limit  is	 specified.  The value of limit can be a number in the
	      unit specified below with each resource, or the value unlimited.
	      The -H and -S options specify whether the hard limit or the soft
	      limit for the given resource is set.  A  hard  limit  cannot  be
	      increased	 once  it is set.  A soft limit can be increased up to
	      the value of the hard limit.  If neither the H nor S  option  is
	      specified,  the  limit  applies  to  both.  The current resource
	      limit is printed when limit is omitted.  In this case, the  soft
	      limit  is	 printed  unless  H  is specified.  When more than one
	      resource is specified, then the limit name and unit  is  printed
	      before the value.
	      -a     Lists all of the current resource limits.
	      -c     The number of 512-byte blocks on the size of core dumps.
	      -d     The number of K-bytes on the size of the data area.
	      -f     The  number of 512-byte blocks on files that can be writ‐
		     ten by the current process or by child  processes	(files
		     of any size may be read).
	      -m     The number of K-bytes on the size of physical memory.
	      -n     The number of file descriptors plus 1.
	      -p     The number of 512-byte blocks for pipe buffering.
	      -s     The number of K-bytes on the size of the stack area.
	      -t     The number of CPU seconds to be used by each process.
	      -v     The number of K-bytes for virtual memory.

	      If no option is given, -f is assumed.

       umask [ -S ] [ mask ]
	      The user file-creation mask is set to mask (see umask(2)).  mask
	      can either be an octal number or a symbolic value	 as  described
	      in  chmod(1).  If a symbolic value is given, the new umask value
	      is the complement of the result of applying mask to the  comple‐
	      ment  of the previous umask value.  If mask is omitted, the cur‐
	      rent value of the mask is printed.  The  -S  option  causes  the
	      mode  to be printed as a symbolic value.	Otherwise, the mask is
	      printed in octal.

       † unalias [ -a ] name ...
	      The aliases given by the list of	names  are  removed  from  the
	      alias list.  The -a option causes all the aliases to be unset.

       †unset [ -fnv ] vname ...
	      The  variables given by the list of vnames are unassigned, i.e.,
	      except  for  sub-variables  within  a  type,  their  values  and
	      attributes  are erased.  For sub-variables of a type, the values
	      are reset to the default value from the type definition.	 Read‐
	      only  variables  cannot be unset.	 If the -f option is set, then
	      the names refer to function names.  If the  -v  option  is  set,
	      then the names refer to variable names.  The -f option overrides
	      -v.  If -n is set and name is a name reference, then  name  will
	      be  unset	 rather	 than  the  variable  that it references.  The
	      default is  equivalent  to  -v.	Unsetting  LINENO,  MAILCHECK,
	      OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their spe‐
	      cial meaning even if they are subsequently assigned to.

       wait [ job ... ]
	      Wait for the specified job and report  its  termination  status.
	      If  job  is not given, then all currently active child processes
	      are waited for.  The exit status from this command  is  that  of
	      the last process waited for if job is specified; otherwise it is
	      zero.  See Jobs for a description of the format of job.

       whence [ -afpv ] name ...
	      For each name, indicate how it would be interpreted if used as a
	      command name.
	      The  -v  option  produces	 a more verbose report.	 The -f option
	      skips the search for functions.	The  -p	 option	 does  a  path
	      search  for  name	 even  if  name	 is an alias, a function, or a
	      reserved word.  The -p option turns off the -v option.   The  -a
	      option  is  similar  to the -v option but causes all interpreta‐
	      tions of the given name to be reported.

   Invocation.
       If the shell is invoked by exec(2), and the first character of argument
       zero  ($0) is -, then the shell is assumed to be a login shell and com‐
       mands are read from /etc/profile and then from either .profile  in  the
       current	directory or $HOME/.profile, if either file exists.  Next, for
       interactive shells, commands are read from the file named by performing
       parameter  expansion, command substitution, and arithmetic substitution
       on the value of the environment variable ENV if the  file  exists.   If
       the  -s	option	is  not	 present and arg and a file by the name of arg
       exists, then it reads and executes  this	 script.   Otherwise,  if  the
       first arg does not contain a /, a path search is performed on the first
       arg to determine the name of the script to  execute.   The  script  arg
       must have execute permission and any setuid and setgid settings will be
       ignored.	 If the script is not found on the path, arg is	 processed  as
       if  it named a built-in command or function.  Commands are then read as
       described below; the following options are  interpreted	by  the	 shell
       when it is invoked:

       -D      Do  not execute the script, but output the set of double quoted
	       strings preceded by a $.	 These strings are needed  for	local‐
	       ization of the script to different locales.
       -E      Reads  the file named by the ENV variable or by $HOME/.kshrc if
	       not defined after the profiles.
       -c	 If the -c option is present, then commands are read from  the
		 first arg.  Any remaining arguments become positional parame‐
		 ters starting at 0.
       -s	 If the -s option is present or if no arguments	 remain,  then
		 commands  are	read  from  the standard input.	 Shell output,
		 except for the output of the Special Commands	listed	above,
		 is written to file descriptor 2.
       -i	 If  the -i option is present or if the shell input and output
		 are attached to a terminal (as told  by  tcgetattr(2)),  then
		 this  shell is interactive.  In this case TERM is ignored (so
		 that kill 0 does not kill an interactive shell) and  INTR  is
		 caught	 and  ignored (so that wait is interruptible).	In all
		 cases, QUIT is ignored by the shell.
       -r	 If the -r option is present, the shell is a restricted shell.
       -D	 A list of all double quoted strings that are preceded by a  $
		 will  be  printed on standard output and the shell will exit.
		 This set of strings will be subject to	 language  translation
		 when  the locale is not C or POSIX.  No commands will be exe‐
		 cuted.

       -P	 If -P or -o profile is present, the shell is a profile	 shell
		 (see pfexec(1)).

       -R filename
		 The  -R filename option is used to generate a cross reference
		 database that can be used by a separate utility to find defi‐
		 nitions and references for variables and commands.

       The remaining options and arguments are described under the set command
       above.  An optional - as the first argument is ignored.

   Rksh Only.
       Rksh is used to set up login names  and	execution  environments	 whose
       capabilities are more controlled than those of the standard shell.  The
       actions of rksh are identical to those of ksh, except that the  follow‐
       ing are disallowed:
	      Unsetting the restricted option.
	      changing directory (see cd(1)),
	      setting  or  unsetting  the  value  or attributes of SHELL, ENV,
	      FPATH, or PATH,
	      specifying path or command names containing /,
	      redirecting output (>, >|, <>, and >>).
	      adding or deleting built-in commands.
	      using command -p to invoke a command.

       The restrictions above are enforced after .profile and  the  ENV	 files
       are interpreted.

       When  a	command	 to be executed is found to be a shell procedure, rksh
       invokes ksh to execute it.  Thus, it is possible to provide to the end-
       user  shell  procedures that have access to the full power of the stan‐
       dard shell, while imposing a limited  menu  of  commands;  this	scheme
       assumes	that  the end-user does not have write and execute permissions
       in the same directory.

       The net effect of these rules is that the writer of  the	 .profile  has
       complete	 control  over	user  actions,	by performing guaranteed setup
       actions and leaving the user in an appropriate directory (probably  not
       the login directory).

       The  system  administrator often sets up a directory of commands (e.g.,
       /usr/rbin) that can be safely invoked by rksh.

EXIT STATUS
       Errors detected by the shell, such as syntax errors, cause the shell to
       return a non-zero exit status.  If the shell is being used non-interac‐
       tively, then execution of the shell file is abandoned unless the	 error
       occurs inside a subshell in which case the subshell is abandoned.  Oth‐
       erwise, the shell returns the exit status of the last command  executed
       (see  also  the	exit  command above).  Run time errors detected by the
       shell are reported by printing the command or  function	name  and  the
       error  condition.   If  the  line  number that the error occurred on is
       greater than one, then the line number is also printed in square brack‐
       ets ([]) after the command or function name.

FILES
       /etc/profile
	      The system wide initialization file, executed for login shells.

       $HOME/.profile
	      The  personal  initialization  file,  executed  for login shells
	      after /etc/profile.

       $HOME/..kshrc
	      Default personal initialization file, executed  for  interactive
	      shells when ENV is not set.

       /etc/suid_profile
	      Alternative  initialization  file,  executed instead of the per‐
	      sonal initialization file when the real and  effective  user  or
	      group id do not match.

       /dev/null
	      NULL device

SEE ALSO
       cat(1),	cd(1),	chmod(1), cut(1), egrep(1), echo(1), emacs(1), env(1),
       fgrep(1), gmacs(1), grep(1), newgrp(1),	pfexec(1),  stty(1),  test(1),
       umask(1),  vi(1),  dup(2),  exec(2),  fork(2),  getpwnam(3),  ioctl(2),
       lseek(2),  paste(1),  pathconf(2),   pipe(2),   sysconf(2),   umask(2),
       ulimit(2),  wait(2),  wctrans(3),  rand(3), a.out(5), profile(5), envi‐
       ron(7).

       Morris I. Bolsky and David G. Korn, The New KornShell Command and  Pro‐
       gramming Language, Prentice Hall, 1995.

       POSIX  -	 Part  2:  Shell  and Utilities, IEEE Std 1003.2-1992, ISO/IEC
       9945-2, IEEE, 1993.

CAVEATS
       If a command is executed, and then a command  with  the	same  name  is
       installed  in a directory in the search path before the directory where
       the original command was found, the shell will  continue	 to  exec  the
       original	 command.   Use	 the -t option of the alias command to correct
       this situation.

       Some very old shell scripts contain a ^ as a synonym for the pipe char‐
       acter ⎪.

       Using  the  hist	 built-in command within a compound command will cause
       the whole command to disappear from the history file.

       The built-in command . file reads the whole file	 before	 any  commands
       are  executed.	Therefore, alias and unalias commands in the file will
       not apply to any commands defined in the file.

       Traps are not processed	while  a  job  is  waiting  for	 a  foreground
       process.	  Thus,	 a trap on CHLD won't be executed until the foreground
       job terminates.

       It is a good idea to leave a space after the comma operator  in	arith‐
       metic  expressions  to  prevent the comma from being interpreted as the
       decimal point character in certain locales.

									KSH(1)
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