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FC(1P)			   POSIX Programmer's Manual			FC(1P)

       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

       fc — process the command history list

       fc [−r] [−e editor] [first [last]]

       fc −l [−nr] [first [last]]

       fc −s [old=new] [first]

       The fc utility shall list, or shall edit and re-execute, commands  pre‐
       viously entered to an interactive sh.

       The  command history list shall reference commands by number. The first
       number in the list is selected arbitrarily. The relationship of a  num‐
       ber to its command shall not change except when the user logs in and no
       other process is accessing the list, at which time the system may reset
       the  numbering  to  start the oldest retained command at another number
       (usually 1). When the number reaches  an	 implementation-defined	 upper
       limit,  which  shall  be no smaller than the value in HISTSIZE or 32767
       (whichever is greater), the shell may wrap the  numbers,	 starting  the
       next  command  with  a  lower number (usually 1). However, despite this
       optional wrapping of  numbers,  fc  shall  maintain  the	 time-ordering
       sequence of the commands. For example, if four commands in sequence are
       given the numbers 32766, 32767, 1 (wrapped), and 2  as  they  are  exe‐
       cuted,  command	32767  is  considered  the command previous to 1, even
       though its number is higher.

       When commands are edited (when the −l option  is	 not  specified),  the
       resulting  lines	 shall	be  entered at the end of the history list and
       then re-executed by sh.	The fc command that caused the	editing	 shall
       not  be entered into the history list. If the editor returns a non-zero
       exit status, this shall suppress the entry into the  history  list  and
       the command re-execution.  Any command line variable assignments or re‐
       direction operators used with fc	 shall	affect	both  the  fc  command
       itself as well as the command that results; for example:

	   fc −s −− −1 2>/dev/null

       reinvokes  the previous command, suppressing standard error for both fc
       and the previous command.

       The fc  utility	shall  conform	to  the	 Base  Definitions  volume  of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       −e editor Use the editor named by editor to edit the commands. The edi‐
		 tor string is a utility name, subject to search via the  PATH
		 variable  (see	 the  Base Definitions volume of POSIX.1‐2008,
		 Chapter 8, Environment Variables).  The value in  the	FCEDIT
		 variable shall be used as a default when −e is not specified.
		 If FCEDIT is null or unset, ed shall be used as the editor.

       −l	 (The letter ell.) List the commands rather than  invoking  an
		 editor on them. The commands shall be written in the sequence
		 indicated by the first and last operands, as affected by  −r,
		 with each command preceded by the command number.

       −n	 Suppress command numbers when listing with −l.

       −r	 Reverse  the order of the commands listed (with −l) or edited
		 (with neither −l nor −s).

       −s	 Re-execute the command without invoking an editor.

       The following operands shall be supported:

       first, last
		 Select the commands to list or edit. The number  of  previous
		 commands  that	 can  be  accessed  shall be determined by the
		 value of the HISTSIZE variable. The value of first or last or
		 both shall be one of the following:

		 [+]number A  positive	number	representing a command number;
			   command  numbers  can  be  displayed	 with  the  −l

		 −number   A  negative decimal number representing the command
			   that was executed number  of	 commands  previously.
			   For	example,  −1  is the immediately previous com‐

		 string	   A string indicating the most recently entered  com‐
			   mand	 that  begins with that string. If the old=new
			   operand is not also specified with −s,  the	string
			   form	 of the first operand cannot contain an embed‐
			   ded <equals-sign>.

		 When the synopsis form with −s is used:

		  *  If first is omitted, the previous command shall be used.

		 For the synopsis forms without −s:

		  *  If last is omitted, last shall default  to	 the  previous
		     command when −l is specified; otherwise, it shall default
		     to first.

		  *  If first and last are both omitted, the previous 16  com‐
		     mands  shall  be  listed  or  the previous single command
		     shall be edited (based on the −l option).

		  *  If first and last are both present, all of	 the  commands
		     from first to last shall be edited (without −l) or listed
		     (with −l).	 Editing multiple  commands  shall  be	accom‐
		     plished  by  presenting to the editor all of the commands
		     at one time, each command starting	 on  a	new  line.  If
		     first  represents a newer command than last, the commands
		     shall be listed or edited in reverse sequence, equivalent
		     to	 using −r.  For example, the following commands on the
		     first line are equivalent to the  corresponding  commands
		     on the second:

			 fc −r 10 20	fc    30 40
			 fc    20 10	fc −r 40 30

		  *  When  a  range  of	 commands  is used, it shall not be an
		     error to specify first or last values that are not in the
		     history  list; fc shall substitute the value representing
		     the oldest or newest command in the list, as appropriate.
		     For  example,  if there are only ten commands in the his‐
		     tory list, numbered 1 to 10:

			 fc −l
			 fc 1 99

		     shall list and edit, respectively, all ten commands.

       old=new	 Replace the first occurrence of string old in the commands to
		 be re-executed by the string new.

       Not used.


       The following environment variables shall affect the execution of fc:

       FCEDIT	 This  variable,  when	expanded by the shell, shall determine
		 the default value for the −e editor option's  editor  option-
		 argument. If FCEDIT is null or unset, ed shall be used as the

       HISTFILE	 Determine a pathname naming a command history	file.  If  the
		 HISTFILE variable is not set, the shell may attempt to access
		 or create a file .sh_history in the directory referred to  by
		 the  HOME  environment	 variable.  If the shell cannot obtain
		 both read and write access to, or create, the	history	 file,
		 it shall use an unspecified mechanism that allows the history
		 to operate properly. (References to history ``file'' in  this
		 section  shall	 be understood to mean this unspecified mecha‐
		 nism in such cases.) An implementation may choose  to	access
		 this  variable	 only when initializing the history file; this
		 initialization shall occur when fc or	sh  first  attempt  to
		 retrieve  entries  from,  or add entries to, the file, as the
		 result of commands issued by the user, the file named by  the
		 ENV   variable,  or  implementation-defined  system  start-up
		 files. In some historical shells, the history	file  is  ini‐
		 tialized  just	 after the ENV file has been processed. There‐
		 fore, it is implementation-defined whether  changes  made  to
		 HISTFILE  after  the  history	file  has been initialized are
		 effective.  Implementations may choose to disable the history
		 list  mechanism  for users with appropriate privileges who do
		 not set HISTFILE; the specific circumstances under which this
		 occurs	 are implementation-defined. If more than one instance
		 of the shell is using the same history file, it  is  unspeci‐
		 fied how updates to the history file from those shells inter‐
		 act. As entries are deleted from the history file, they shall
		 be  deleted oldest first. It is unspecified when history file
		 entries are physically removed from the history file.

       HISTSIZE	 Determine a decimal number representing the limit to the num‐
		 ber  of  previous commands that are accessible. If this vari‐
		 able is unset, an unspecified default greater than  or	 equal
		 to  128  shall be used. The maximum number of commands in the
		 history list is unspecified, but shall be at  least  128.  An
		 implementation	 may  choose to access this variable only when
		 initializing the history file, as described  under  HISTFILE.
		 Therefore, it is unspecified whether changes made to HISTSIZE
		 after the history file has been initialized are effective.

       LANG	 Provide a default value for  the  internationalization	 vari‐
		 ables	that are unset or null. (See the Base Definitions vol‐
		 ume of POSIX.1‐2008, Section 8.2, Internationalization	 Vari‐
		 ables	for  the  precedence of internationalization variables
		 used to determine the values of locale categories.)

       LC_ALL	 If set to a non-empty string value, override  the  values  of
		 all the other internationalization variables.

       LC_CTYPE	 Determine  the	 locale for the interpretation of sequences of
		 bytes of text data as characters (for example, single-byte as
		 opposed  to  multi-byte  characters  in  arguments  and input

		 Determine the locale that should be used to affect the format
		 and  contents	of  diagnostic	messages  written  to standard

       NLSPATH	 Determine the location of message catalogs for the processing


       When the −l option is used to list commands, the format of each command
       in the list shall be as follows:

	   "%d\t%s\n", <line number>, <command>

       If both the −l and −n options are specified, the format of each command
       shall be:

	   "\t%s\n", <command>

       If  the	<command>  consists of more than one line, the lines after the
       first shall be displayed as:

	   "\t%s\n", <continued-command>

       The standard error shall be used only for diagnostic messages.



       The following exit values shall be returned:

	0    Successful completion of the listing.

       >0    An error occurred.

       Otherwise, the exit status shall be that of the	commands  executed  by


       The following sections are informative.

       Since editors sometimes use file descriptors as integral parts of their
       editing, redirecting their file descriptors as part of the  fc  command
       can  produce  unexpected results. For example, if vi is the FCEDIT edi‐
       tor, the command:

	   fc −s | more

       does not work correctly on many systems.

       Users on windowing systems may want to have separate history files  for
       each window by setting HISTFILE as follows:



       This utility is based on the fc built-in of the KornShell.

       An  early  proposal specified the −e option as [−e editor [old= new ]],
       which is not historical practice. Historical practice in fc  of	either
       [−e  editor]  or	 [−e  −	 [  old=  new  ]]  is acceptable, but not both
       together. To clarify this, a new option −s was introduced replacing the
       [−e −].	This resolves the conflict and makes fc conform to the Utility
       Syntax Guidelines.

       HISTFILE	 Some implementations of the KornShell check for the superuser
		 and do not create a history file unless HISTFILE is set. This
		 is done primarily to avoid creating  unlinked	files  in  the
		 root  file  system  when  logging in during single-user mode.
		 HISTFILE must be set for the superuser to have history.

       HISTSIZE	 Needed to limit the size of history files. It is  the	intent
		 of  the  standard  developers	that when two shells share the
		 same history file, commands that are  entered	in  one	 shell
		 shall be accessible by the other shell. Because of the diffi‐
		 culties of synchronization over a network, the	 exact	nature
		 of the interaction is unspecified.

       The initialization process for the history file can be dependent on the
       system start-up files, in that they may contain	commands  that	effec‐
       tively  preempt	the  settings  the user has for HISTFILE and HISTSIZE.
       For example, function definition commands are recorded in  the  history
       file. If the system administrator includes function definitions in some
       system start-up file called before the ENV file, the  history  file  is
       initialized  before the user can influence its characteristics. In some
       historical shells, the history file is initialized just after  the  ENV
       file has been processed. Because of these situations, the text requires
       the initialization process to be implementation-defined.

       Consideration was given to omitting the fc utility in favor of the com‐
       mand line editing feature in sh.	 For example, in vi editing mode, typ‐
       ing "<ESC>v" is equivalent to:

	   EDITOR=vi fc

       However, the fc utility allows the user the flexibility to edit	multi‐
       ple commands simultaneously (such as fc 10 20) and to use editors other
       than those supported by sh for command line editing.

       In the KornShell, the alias r (``re-do'') is preset to fc −e − (equiva‐
       lent  to	 the POSIX fc −s).  This is probably an easier command name to
       remember than fc (``fix command''), but it does not  meet  the  Utility
       Syntax  Guidelines.   Renaming  fc  to hist or redo was considered, but
       since this description closely matches  historical  KornShell  practice
       already,	 such  a  renaming  was seen as gratuitous.  Users are free to
       create aliases whenever odd historical names  such  as  fc,  awk,  cat,
       grep, or yacc are standardized by POSIX.

       Command numbers have no ordering effects; they are like serial numbers.
       The −r option and −number operand address the sequence of command  exe‐
       cution,	regardless  of serial numbers. So, for example, if the command
       number wrapped back to 1 at some arbitrary point,  there	 would	be  no
       ambiguity  associated  with  traversing the wrap point. For example, if
       the command history were:

	   32766: echo 1
	   32767: echo 2
	   1: echo 3

       the number −2 refers to command 32767 because it is the second previous
       command, regardless of serial number.



       The  Base  Definitions  volume  of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal and Electronics Engineers,  Inc  and	 The  Open  Group.   (This  is
       POSIX.1-2008  with  the	2013  Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained	online
       at http://www.unix.org/online.html .

       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013				FC(1P)

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