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GAWK(1)			       Utility Commands			       GAWK(1)

       gawk - pattern scanning and processing language

       gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       gawk [ POSIX or GNU style options ] [ -- ] program-text file ...

       pgawk [ POSIX or GNU style options ] -f program-file [ -- ] file ...
       pgawk [ POSIX or GNU style options ] [ -- ] program-text file ...

       Gawk  is	 the  GNU Project's implementation of the AWK programming lan‐
       guage.  It conforms to the definition of	 the  language	in  the	 POSIX
       1003.2  Command	Language And Utilities Standard.  This version in turn
       is based on the description in The AWK Programming  Language,  by  Aho,
       Kernighan,  and	Weinberger,  with the additional features found in the
       System V Release 4 version of UNIX awk.	Gawk also provides more recent
       Bell  Laboratories  awk extensions, and a number of GNU-specific exten‐

       Pgawk is the profiling version of gawk.	It is identical in  every  way
       to  gawk,  except  that	programs run more slowly, and it automatically
       produces an execution profile in the file awkprof.out when  done.   See
       the --profile option, below.

       The  command  line  consists of options to gawk itself, the AWK program
       text (if not supplied via the -f or --file options), and values	to  be
       made available in the ARGC and ARGV pre-defined AWK variables.

       Gawk options may be either traditional POSIX one letter options, or GNU
       style long options.  POSIX options start with a single “-”, while  long
       options	start  with “--”.  Long options are provided for both GNU-spe‐
       cific features and for POSIX-mandated features.

       Following the POSIX standard, gawk-specific options  are	 supplied  via
       arguments  to  the -W option.  Multiple -W options may be supplied Each
       -W option has a corresponding long option, as  detailed	below.	 Argu‐
       ments  to  long options are either joined with the option by an = sign,
       with no intervening spaces, or they may be provided in the next command
       line  argument.	Long options may be abbreviated, as long as the abbre‐
       viation remains unique.

       Gawk accepts the following options, listed alphabetically.

       -F fs
       --field-separator fs
	      Use fs for the input field separator (the value of the FS prede‐
	      fined variable).

       -v var=val
       --assign var=val
	      Assign  the  value  val to the variable var, before execution of
	      the program begins.  Such variable values are available  to  the
	      BEGIN block of an AWK program.

       -f program-file
       --file program-file
	      Read  the AWK program source from the file program-file, instead
	      of from the  first  command  line	 argument.   Multiple  -f  (or
	      --file) options may be used.

       -mf NNN
       -mr NNN
	      Set various memory limits to the value NNN.  The f flag sets the
	      maximum number of fields, and the r flag sets the maximum record
	      size.  These two flags and the -m option are from the Bell Labo‐
	      ratories research version of UNIX	 awk.	They  are  ignored  by
	      gawk, since gawk has no pre-defined limits.

       -W compat
       -W traditional
	      Run  in compatibility mode.  In compatibility mode, gawk behaves
	      identically to UNIX awk; none of the GNU-specific extensions are
	      recognized.   The	 use  of  --traditional	 is preferred over the
	      other forms of this option.  See GNU EXTENSIONS, below, for more

       -W copyleft
       -W copyright
	      Print the short version of the GNU copyright information message
	      on the standard output and exit successfully.

       -W dump-variables[=file]
	      Print a sorted list of global variables, their types  and	 final
	      values  to file.	If no file is provided, gawk uses a file named
	      awkvars.out in the current directory.
	      Having a list of all the global variables is a good way to  look
	      for  typographical  errors in your programs.  You would also use
	      this option if you have a large program with a lot of functions,
	      and  you want to be sure that your functions don't inadvertently
	      use global variables that you meant to be	 local.	  (This	 is  a
	      particularly  easy  mistake  to  make with simple variable names
	      like i, j, and so on.)

       -W help
       -W usage
	      Print a relatively short summary of the available options on the
	      standard	output.	  (Per the GNU Coding Standards, these options
	      cause an immediate, successful exit.)

       -W lint[=value]
	      Provide warnings about constructs that are dubious or non-porta‐
	      ble  to other AWK implementations.  With an optional argument of
	      fatal, lint warnings become fatal errors.	 This may be  drastic,
	      but  its use will certainly encourage the development of cleaner
	      AWK programs.  With an optional argument of invalid, only	 warn‐
	      ings about things that are actually invalid are issued. (This is
	      not fully implemented yet.)

       -W lint-old
	      Provide warnings about constructs that are not portable  to  the
	      original version of Unix awk.

       -W gen-po
	      Scan  and	 parse	the AWK program, and generate a GNU .po format
	      file on standard output with entries for all localizable strings
	      in  the  program.	  The program itself is not executed.  See the
	      GNU gettext distribution for more information on .po files.

       -W non-decimal-data
	      Recognize octal and hexadecimal values in input data.  Use  this
	      option with great caution!

       -W posix
	      This  turns on compatibility mode, with the following additional

	      · \x escape sequences are not recognized.

	      · Only space and tab act as field separators when FS is set to a
		single space, newline does not.

	      · You cannot continue lines after ?  and :.

	      · The synonym func for the keyword function is not recognized.

	      · The operators ** and **= cannot be used in place of ^ and ^=.

	      · The fflush() function is not available.

       -W profile[=prof_file]
	      Send  profiling  data to prof_file.  The default is awkprof.out.
	      When run with gawk, the profile is just a “pretty printed”  ver‐
	      sion  of the program.  When run with pgawk, the profile contains
	      execution counts of each statement in the program	 in  the  left
	      margin and function call counts for each user-defined function.

       -W re-interval
	      Enable  the  use	of  interval expressions in regular expression
	      matching (see Regular Expressions, below).  Interval expressions
	      were not traditionally available in the AWK language.  The POSIX
	      standard added them, to make awk and egrep consistent with  each
	      other.   However, their use is likely to break old AWK programs,
	      so gawk only provides them  if  they  are	 requested  with  this
	      option, or when --posix is specified.

       -W source program-text
       --source program-text
	      Use program-text as AWK program source code.  This option allows
	      the easy intermixing of library functions (used via the  -f  and
	      --file  options)	with  source code entered on the command line.
	      It is intended primarily for medium to large AWK	programs  used
	      in shell scripts.

       -W version
	      Print  version  information  for this particular copy of gawk on
	      the standard output.  This is useful mainly for knowing  if  the
	      current  copy  of gawk on your system is up to date with respect
	      to whatever the Free Software Foundation is distributing.	  This
	      is  also	useful when reporting bugs.  (Per the GNU Coding Stan‐
	      dards, these options cause an immediate, successful exit.)

       --     Signal the end of options. This is useful to allow further argu‐
	      ments  to	 the  AWK program itself to start with a “-”.  This is
	      mainly for consistency with the argument parsing convention used
	      by most other POSIX programs.
       In  compatibility  mode,	 any other options are flagged as invalid, but
       are otherwise ignored.  In normal operation, as long  as	 program  text
       has  been supplied, unknown options are passed on to the AWK program in
       the ARGV array for processing.  This is particularly useful for running
       AWK programs via the “#!” executable interpreter mechanism.
       An  AWK program consists of a sequence of pattern-action statements and
       optional function definitions.
	      pattern	{ action statements }
	      function name(parameter list) { statements }
       Gawk first reads the program source from the program-file(s) if	speci‐
       fied, from arguments to --source, or from the first non-option argument
       on the command line.  The -f and --source options may be used  multiple
       times  on  the command line.  Gawk reads the program text as if all the
       program-files and command  line	source	texts  had  been  concatenated
       together.   This	 is  useful  for  building libraries of AWK functions,
       without having to include them in each new AWK program that uses	 them.
       It also provides the ability to mix library functions with command line
       The environment variable AWKPATH specifies a search path	 to  use  when
       finding	source	files named with the -f option.	 If this variable does
       not exist, the default path is ".:/usr/local/share/awk".	  (The	actual
       directory  may  vary, depending upon how gawk was built and installed.)
       If a file name given to the -f option contains a “/” character, no path
       search is performed.
       Gawk executes AWK programs in the following order.  First, all variable
       assignments specified via the -v option are performed.  Next, gawk com‐
       piles  the program into an internal form.  Then, gawk executes the code
       in the BEGIN block(s) (if any), and then proceeds  to  read  each  file
       named  in  the  ARGV array.  If there are no files named on the command
       line, gawk reads the standard input.
       If a filename on the command line has the form var=val it is treated as
       a  variable  assignment.	  The  variable var will be assigned the value
       val.  (This happens after any BEGIN block(s) have been  run.)   Command
       line  variable assignment is most useful for dynamically assigning val‐
       ues to the variables AWK uses to	 control  how  input  is  broken  into
       fields  and records.  It is also useful for controlling state if multi‐
       ple passes are needed over a single data file.
       If the value of a particular element of ARGV is empty (""), gawk	 skips
       over it.
       For  each record in the input, gawk tests to see if it matches any pat‐
       tern in the AWK program.	 For each pattern that the record matches, the
       associated  action  is  executed.  The patterns are tested in the order
       they occur in the program.
       Finally, after all the input is exhausted, gawk executes	 the  code  in
       the END block(s) (if any).
       AWK variables are dynamic; they come into existence when they are first
       used.  Their values are either floating-point numbers  or  strings,  or
       both,  depending	 upon how they are used.  AWK also has one dimensional
       arrays; arrays with multiple dimensions may be simulated.  Several pre-
       defined variables are set as a program runs; these will be described as
       needed and summarized below.
       Normally, records are separated by newline characters.  You can control
       how  records are separated by assigning values to the built-in variable
       RS.  If RS is any single character, that character  separates  records.
       Otherwise,  RS is a regular expression.	Text in the input that matches
       this regular expression separates the record.  However, in  compatibil‐
       ity mode, only the first character of its string value is used for sep‐
       arating records.	 If RS is set to the null  string,  then  records  are
       separated  by blank lines.  When RS is set to the null string, the new‐
       line character always acts as a field separator, in addition  to	 what‐
       ever value FS may have.
       As each input record is read, gawk splits the record into fields, using
       the value of the FS variable as the field separator.  If FS is a single
       character,  fields  are separated by that character.  If FS is the null
       string, then each individual character becomes a separate field.	  Oth‐
       erwise, FS is expected to be a full regular expression.	In the special
       case that FS is a single space, fields are separated by runs of	spaces
       and/or  tabs  and/or  newlines.	 (But  see  the discussion of --posix,
       below).	NOTE: The value of IGNORECASE (see  below)  also  affects  how
       fields  are  split when FS is a regular expression, and how records are
       separated when RS is a regular expression.
       If the FIELDWIDTHS variable is set to a space separated	list  of  num‐
       bers,  each  field  is expected to have fixed width, and gawk splits up
       the record using the specified widths.  The value  of  FS  is  ignored.
       Assigning  a  new  value	 to  FS	 overrides the use of FIELDWIDTHS, and
       restores the default behavior.
       Each field in the input record may be referenced by its	position,  $1,
       $2,  and so on.	$0 is the whole record.	 Fields need not be referenced
       by constants:
	      n = 5
	      print $n
       prints the fifth field in the input record.
       The variable NF is set to the total  number  of	fields	in  the	 input
       References  to  non-existent fields (i.e. fields after $NF) produce the
       null-string.  However, assigning to a non-existent field (e.g., $(NF+2)
       = 5) increases the value of NF, creates any intervening fields with the
       null string as their value, and causes the value of  $0	to  be	recom‐
       puted, with the fields being separated by the value of OFS.  References
       to negative numbered fields  cause  a  fatal  error.   Decrementing  NF
       causes  the  values  of	fields	past the new value to be lost, and the
       value of $0 to be recomputed, with the fields being  separated  by  the
       value of OFS.
       Assigning  a  value  to an existing field causes the whole record to be
       rebuilt when $0 is referenced.  Similarly,  assigning  a	 value	to  $0
       causes the record to be resplit, creating new values for the fields.
   Built-in Variables
       Gawk's built-in variables are:
       ARGC	   The	number	of  command  line  arguments (does not include
		   options to gawk, or the program source).
       ARGIND	   The index in ARGV of the current file being processed.
       ARGV	   Array of command line arguments.  The array is indexed from
		   0  to  ARGC - 1.  Dynamically changing the contents of ARGV
		   can control the files used for data.
       BINMODE	   On non-POSIX systems, specifies use of  “binary”  mode  for
		   all	file  I/O.  Numeric values of 1, 2, or 3, specify that
		   input files, output	files,	or  all	 files,	 respectively,
		   should  use binary I/O.  String values of "r", or "w" spec‐
		   ify that input files, or output files, respectively, should
		   use binary I/O.  String values of "rw" or "wr" specify that
		   all files should use binary I/O.  Any other string value is
		   treated as "rw", but generates a warning message.
       CONVFMT	   The conversion format for numbers, "%.6g", by default.
       ENVIRON	   An  array containing the values of the current environment.
		   The array is indexed by  the	 environment  variables,  each
		   element  being  the	value  of  that	 variable (e.g., ENVI‐
		   RON["HOME"] might be /home/arnold).	 Changing  this	 array
		   does not affect the environment seen by programs which gawk
		   spawns via redirection or the system() function.
       ERRNO	   If a system error occurs either  doing  a  redirection  for
		   getline,  during  a	read for getline, or during a close(),
		   then ERRNO will contain a string describing the error.  The
		   value is subject to translation in non-English locales.
       FIELDWIDTHS A  white-space  separated  list  of fieldwidths.  When set,
		   gawk parses the input into fields of fixed  width,  instead
		   of  using the value of the FS variable as the field separa‐
       FILENAME	   The name of the current input file.	If no files are speci‐
		   fied	 on  the  command  line, the value of FILENAME is “-”.
		   However, FILENAME  is  undefined  inside  the  BEGIN	 block
		   (unless set by getline).
       FNR	   The input record number in the current input file.
       FS	   The input field separator, a space by default.  See Fields,
       IGNORECASE  Controls the case-sensitivity of all regular expression and
		   string  operations.	 If  IGNORECASE	 has a non-zero value,
		   then string comparisons  and	 pattern  matching  in	rules,
		   field splitting with FS, record separating with RS, regular
		   expression matching	with  ~	 and  !~,  and	the  gensub(),
		   gsub(), index(), match(), split(), and sub() built-in func‐
		   tions all ignore case when doing regular expression	opera‐
		   tions.  NOTE: Array subscripting is not affected.  However,
		   the asort() and asorti() functions are affected.
		   Thus, if IGNORECASE is not equal to zero, /aB/ matches  all
		   of the strings "ab", "aB", "Ab", and "AB".  As with all AWK
		   variables, the initial value of IGNORECASE is zero, so  all
		   regular expression and string operations are normally case-
		   sensitive.  Under Unix, the full ISO 8859-1 Latin-1 charac‐
		   ter set is used when ignoring case.
       LINT	   Provides  dynamic  control of the --lint option from within
		   an AWK program.  When true, gawk prints lint warnings. When
		   false,  it  does  not.   When  assigned  the	 string	 value
		   "fatal", lint warnings become fatal	errors,	 exactly  like
		   --lint=fatal.  Any other true value just prints warnings.
       NF	   The number of fields in the current input record.
       NR	   The total number of input records seen so far.
       OFMT	   The output format for numbers, "%.6g", by default.
       OFS	   The output field separator, a space by default.
       ORS	   The output record separator, by default a newline.
       PROCINFO	   The	elements  of  this array provide access to information
		   about the running AWK program.  On some systems, there  may
		   be  elements	 in  the  array, "group1" through "groupn" for
		   some n, which is the number of  supplementary  groups  that
		   the	process	 has.	Use  the in operator to test for these
		   elements.  The following  elements  are  guaranteed	to  be
		   PROCINFO["egid"]   the value of the getegid(2) system call.
		   PROCINFO["euid"]   the value of the geteuid(2) system call.
		   PROCINFO["FS"]     "FS"  if	field  splitting with FS is in
				      effect, or "FIELDWIDTHS" if field split‐
				      ting with FIELDWIDTHS is in effect.
		   PROCINFO["gid"]    the value of the getgid(2) system call.
		   PROCINFO["pgrpid"] the  process  group  ID  of  the current
		   PROCINFO["pid"]    the process ID of the current process.
		   PROCINFO["ppid"]   the parent process  ID  of  the  current
		   PROCINFO["uid"]    the value of the getuid(2) system call.
       RS	   The input record separator, by default a newline.
       RT	   The record terminator.  Gawk sets RT to the input text that
		   matched the character or regular  expression	 specified  by
       RSTART	   The	index  of the first character matched by match(); 0 if
		   no match.  (This implies that character  indices  start  at
       RLENGTH	   The	length	of  the	 string	 matched  by match(); -1 if no
       SUBSEP	   The character used to separate multiple subscripts in array
		   elements, by default "\034".
       TEXTDOMAIN  The text domain of the AWK program; used to find the local‐
		   ized translations for the program's strings.
       Arrays are subscripted with an expression between  square  brackets  ([
       and ]).	If the expression is an expression list (expr, expr ...)  then
       the array subscript is a string consisting of the concatenation of  the
       (string) value of each expression, separated by the value of the SUBSEP
       variable.  This facility	 is  used  to  simulate	 multiply  dimensioned
       arrays.	For example:
	      i = "A"; j = "B"; k = "C"
	      x[i, j, k] = "hello, world\n"
       assigns the string "hello, world\n" to the element of the array x which
       is indexed by the string "A\034B\034C".	All arrays in AWK are associa‐
       tive, i.e. indexed by string values.
       The  special operator in may be used in an if or while statement to see
       if an array has an index consisting of a particular value.
	      if (val in array)
		   print array[val]
       If the array has multiple subscripts, use (i, j) in array.
       The in construct may also be used in a for loop to iterate over all the
       elements of an array.
       An  element  may	 be  deleted from an array using the delete statement.
       The delete statement may also be used to delete the entire contents  of
       an array, just by specifying the array name without a subscript.
   Variable Typing And Conversion
       Variables  and  fields  may be (floating point) numbers, or strings, or
       both.  How the value of a variable is interpreted depends upon its con‐
       text.  If used in a numeric expression, it will be treated as a number,
       if used as a string it will be treated as a string.
       To force a variable to be treated as a number, add 0 to it; to force it
       to be treated as a string, concatenate it with the null string.
       When  a	string must be converted to a number, the conversion is accom‐
       plished using strtod(3).	 A number is converted to a  string  by	 using
       the  value  of  CONVFMT	as  a  format  string for sprintf(3), with the
       numeric value of the variable as the argument.	However,  even	though
       all  numbers in AWK are floating-point, integral values are always con‐
       verted as integers.  Thus, given
	      CONVFMT = "%2.2f"
	      a = 12
	      b = a ""
       the variable b has a string value of "12" and not "12.00".
       Gawk performs comparisons as follows: If	 two  variables	 are  numeric,
       they  are  compared numerically.	 If one value is numeric and the other
       has a string value that is a “numeric  string,”	then  comparisons  are
       also  done numerically.	Otherwise, the numeric value is converted to a
       string and a string comparison is performed.  Two strings are compared,
       of  course,  as strings.	 Note that the POSIX standard applies the con‐
       cept of “numeric string” everywhere, even to  string  constants.	  How‐
       ever,  this  is	clearly incorrect, and gawk does not do this.  (Fortu‐
       nately, this is fixed in the next version of the standard.)
       Note that string constants, such as "57", are not numeric strings, they
       are  string  constants.	 The  idea of “numeric string” only applies to
       fields, getline input, FILENAME, ARGV elements,	ENVIRON	 elements  and
       the  elements  of an array created by split() that are numeric strings.
       The basic idea is that user input, and  only  user  input,  that	 looks
       numeric, should be treated that way.
       Uninitialized  variables	 have the numeric value 0 and the string value
       "" (the null, or empty, string).
   Octal and Hexadecimal Constants
       Starting with version 3.1 of gawk , you may use C-style octal and hexa‐
       decimal	constants  in  your AWK program source code.  For example, the
       octal value 011 is equal to decimal 9, and the hexadecimal  value  0x11
       is equal to decimal 17.
   String Constants
       String  constants  in  AWK are sequences of characters enclosed between
       double quotes (").  Within strings, certain escape sequences are recog‐
       nized, as in C.	These are:
       \\   A literal backslash.
       \a   The “alert” character; usually the ASCII BEL character.
       \b   backspace.
       \f   form-feed.
       \n   newline.
       \r   carriage return.
       \t   horizontal tab.
       \v   vertical tab.
       \xhex digits
	    The character represented by the string of hexadecimal digits fol‐
	    lowing the \x.  As in ANSI C, all following hexadecimal digits are
	    considered part of the escape sequence.  (This feature should tell
	    us something about language design by committee.)  E.g., "\x1B" is
	    the ASCII ESC (escape) character.
       \ddd The	 character  represented	 by the 1-, 2-, or 3-digit sequence of
	    octal digits.  E.g., "\033" is the ASCII ESC (escape) character.
       \c   The literal character c.
       The escape sequences may also be used inside constant  regular  expres‐
       sions (e.g., /[ \t\f\n\r\v]/ matches whitespace characters).
       In compatibility mode, the characters represented by octal and hexadec‐
       imal escape sequences  are  treated  literally  when  used  in  regular
       expression constants.  Thus, /a\52b/ is equivalent to /a\*b/.
       AWK is a line-oriented language.	 The pattern comes first, and then the
       action.	Action statements are enclosed in { and }.  Either the pattern
       may be missing, or the action may be missing, but, of course, not both.
       If the pattern is missing, the action  is  executed  for	 every	single
       record of input.	 A missing action is equivalent to
	      { print }
       which prints the entire record.
       Comments	 begin	with  the “#” character, and continue until the end of
       the line.  Blank lines may be used to separate statements.  Normally, a
       statement  ends with a newline, however, this is not the case for lines
       ending in a “,”, {, ?, :, &&, or ||.  Lines ending in do or  else  also
       have  their  statements	automatically continued on the following line.
       In other cases, a line can be continued by ending it  with  a  “\”,  in
       which case the newline will be ignored.
       Multiple	 statements  may  be put on one line by separating them with a
       “;”.  This applies to both the statements within the action part	 of  a
       pattern-action  pair (the usual case), and to the pattern-action state‐
       ments themselves.
       AWK patterns may be one of the following:
	      /regular expression/
	      relational expression
	      pattern && pattern
	      pattern || pattern
	      pattern ? pattern : pattern
	      ! pattern
	      pattern1, pattern2
       BEGIN and END are two special kinds of patterns which  are  not	tested
       against	the  input.  The action parts of all BEGIN patterns are merged
       as if all the statements had been written  in  a	 single	 BEGIN	block.
       They  are executed before any of the input is read.  Similarly, all the
       END blocks are merged, and executed when all the input is exhausted (or
       when  an exit statement is executed).  BEGIN and END patterns cannot be
       combined with other patterns in pattern	expressions.   BEGIN  and  END
       patterns cannot have missing action parts.
       For /regular expression/ patterns, the associated statement is executed
       for each input record that matches  the	regular	 expression.   Regular
       expressions  are	 the  same  as	those  in egrep(1), and are summarized
       A relational expression may use any of the operators defined  below  in
       the  section  on	 actions.  These generally test whether certain fields
       match certain regular expressions.
       The &&, ||, and !  operators are logical AND, logical OR,  and  logical
       NOT,  respectively, as in C.  They do short-circuit evaluation, also as
       in C, and are used for combining more  primitive	 pattern  expressions.
       As  in  most  languages, parentheses may be used to change the order of
       The ?: operator is like the same operator in C.	If the	first  pattern
       is true then the pattern used for testing is the second pattern, other‐
       wise it is the third.  Only one of the second  and  third  patterns  is
       The pattern1, pattern2 form of an expression is called a range pattern.
       It matches all input records starting with a record that	 matches  pat‐
       tern1,  and continuing until a record that matches pattern2, inclusive.
       It does not combine with any other sort of pattern expression.
   Regular Expressions
       Regular expressions are the extended kind found	in  egrep.   They  are
       composed of characters as follows:
       c	  matches the non-metacharacter c.
       \c	  matches the literal character c.
       .	  matches any character including newline.
       ^	  matches the beginning of a string.
       $	  matches the end of a string.
       [abc...]	  character list, matches any of the characters abc....
       [^abc...]  negated character list, matches any character except abc....
       r1|r2	  alternation: matches either r1 or r2.
       r1r2	  concatenation: matches r1, and then r2.
       r+	  matches one or more r's.
       r*	  matches zero or more r's.
       r?	  matches zero or one r's.
       (r)	  grouping: matches r.
       r{n,m}	  One  or two numbers inside braces denote an interval expres‐
		  sion.	 If there is one number in the braces,	the  preceding
		  regular  expression r is repeated n times.  If there are two
		  numbers separated by a comma, r is repeated n	 to  m	times.
		  If  there  is	 one  number  followed	by  a comma, then r is
		  repeated at least n times.
		  Interval expressions are only available if either --posix or
		  --re-interval is specified on the command line.

       \y	  matches  the empty string at either the beginning or the end
		  of a word.

       \B	  matches the empty string within a word.

       \<	  matches the empty string at the beginning of a word.

       \>	  matches the empty string at the end of a word.

       \w	  matches any word-constituent character  (letter,  digit,  or

       \W	  matches any character that is not word-constituent.

       \`	  matches  the	empty  string  at  the	beginning  of a buffer

       \'	  matches the empty string at the end of a buffer.

       The escape sequences that are valid in string constants (see below) are
       also valid in regular expressions.

       Character  classes  are a new feature introduced in the POSIX standard.
       A character class is a special notation for describing lists of charac‐
       ters  that  have	 a specific attribute, but where the actual characters
       themselves can vary from country to country and/or from	character  set
       to  character  set.   For  example, the notion of what is an alphabetic
       character differs in the USA and in France.

       A character class is only valid in  a  regular  expression  inside  the
       brackets	 of a character list.  Character classes consist of [:, a key‐
       word denoting the class, and :].	 The character classes defined by  the
       POSIX standard are:

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

       [:graph:]  Characters that are both printable and visible.  (A space is
		  printable, but not visible, while an a is both.)

       [:lower:]  Lower-case alphabetic characters.

       [:print:]  Printable characters (characters that are not control	 char‐

       [:punct:]  Punctuation characters (characters that are not letter, dig‐
		  its, control characters, or space characters).

       [:space:]  Space characters (such as space, tab, and formfeed, to  name
		  a few).

       [:upper:]  Upper-case alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

       For  example,  before the POSIX standard, to match alphanumeric charac‐
       ters, you would have had to write /[A-Za-z0-9]/.	 If your character set
       had  other  alphabetic characters in it, this would not match them, and
       if your character set collated differently from ASCII, this  might  not
       even match the ASCII alphanumeric characters.  With the POSIX character
       classes, you can write /[[:alnum:]]/, and this matches  the  alphabetic
       and numeric characters in your character set.

       Two  additional special sequences can appear in character lists.	 These
       apply to non-ASCII  character  sets,  which  can	 have  single  symbols
       (called	collating  elements)  that  are represented with more than one
       character, as well as several characters that are equivalent  for  col‐
       lating,	or  sorting,  purposes.	  (E.g.,  in French, a plain “e” and a
       grave-accented e` are equivalent.)

       Collating Symbols
	      A	 collating  symbol  is	a  multi-character  collating  element
	      enclosed	in [.  and .].	For example, if ch is a collating ele‐
	      ment, then [[.ch.]]  is a regular expression that	 matches  this
	      collating	 element,  while  [ch]	is  a  regular expression that
	      matches either c or h.

       Equivalence Classes
	      An equivalence class is a locale-specific name  for  a  list  of
	      characters  that are equivalent.	The name is enclosed in [= and
	      =].  For example, the name e might be used to represent  all  of
	      “e,”  “´,”  and “`.”  In this case, [[=e=]] is a regular expres‐
	      sion that matches any of e, ´, or `.

       These features are very valuable in non-English speaking locales.   The
       library	functions  that gawk uses for regular expression matching cur‐
       rently only recognize POSIX character classes; they  do	not  recognize
       collating symbols or equivalence classes.

       The  \y, \B, \<, \>, \w, \W, \`, and \' operators are specific to gawk;
       they are extensions based on facilities in the GNU  regular  expression

       The various command line options control how gawk interprets characters
       in regular expressions.

       No options
	      In the default case, gawk provide all the	 facilities  of	 POSIX
	      regular  expressions  and	 the  GNU regular expression operators
	      described above.	However, interval  expressions	are  not  sup‐

	      Only  POSIX regular expressions are supported, the GNU operators
	      are not special.	(E.g., \w  matches  a  literal	w).   Interval
	      expressions are allowed.

	      Traditional  Unix	 awk regular expressions are matched.  The GNU
	      operators are not special, interval expressions are  not	avail‐
	      able,  and  neither are the POSIX character classes ([[:alnum:]]
	      and so on).   Characters	described  by  octal  and  hexadecimal
	      escape  sequences	 are treated literally, even if they represent
	      regular expression metacharacters.

	      Allow interval  expressions  in  regular	expressions,  even  if
	      --traditional has been provided.

       Action  statements  are enclosed in braces, { and }.  Action statements
       consist of the usual assignment, conditional,  and  looping  statements
       found  in  most	languages.   The  operators,  control  statements, and
       input/output statements available are patterned after those in C.

       The operators in AWK, in order of decreasing precedence, are

       (...)	   Grouping

       $	   Field reference.

       ++ --	   Increment and decrement, both prefix and postfix.

       ^	   Exponentiation (** may  also	 be  used,  and	 **=  for  the
		   assignment operator).

       + - !	   Unary plus, unary minus, and logical negation.

       * / %	   Multiplication, division, and modulus.

       + -	   Addition and subtraction.

       space	   String concatenation.

       < >
       <= >=
       != ==	   The regular relational operators.

       ~ !~	   Regular  expression match, negated match.  NOTE: Do not use
		   a constant regular expression (/foo/) on the left-hand side
		   of  a  ~  or !~.  Only use one on the right-hand side.  The
		   expression /foo/ ~ exp has  the  same  meaning  as  (($0  ~
		   /foo/) ~ exp).  This is usually not what was intended.

       in	   Array membership.

       &&	   Logical AND.

       ||	   Logical OR.

       ?:	   The	C  conditional	expression.  This has the form expr1 ?
		   expr2 : expr3.  If expr1 is true, the value of the  expres‐
		   sion	 is  expr2,  otherwise it is expr3.  Only one of expr2
		   and expr3 is evaluated.

       = += -=
       *= /= %= ^= Assignment.	Both absolute assignment  (var	=  value)  and
		   operator-assignment (the other forms) are supported.

   Control Statements
       The control statements are as follows:

	      if (condition) statement [ else statement ]
	      while (condition) statement
	      do statement while (condition)
	      for (expr1; expr2; expr3) statement
	      for (var in array) statement
	      delete array[index]
	      delete array
	      exit [ expression ]
	      { statements }

   I/O Statements
       The input/output statements are as follows:

       close(file [, how])   Close file, pipe or co-process.  The optional how
			     should only be used when closing  one  end	 of  a
			     two-way  pipe  to	a  co-process.	 It  must be a
			     string value, either "to" or "from".

       getline		     Set $0 from next input record; set NF, NR, FNR.

       getline <file	     Set $0 from next record of file; set NF.

       getline var	     Set var from next input record; set NR, FNR.

       getline var <file     Set var from next record of file.

       command | getline [var]
			     Run command piping the output either into	$0  or
			     var, as above.

       command |& getline [var]
			     Run  command  as  a  co-process piping the output
			     either into $0 or var,  as	 above.	  Co-processes
			     are a gawk extension.

       next		     Stop  processing  the  current input record.  The
			     next input record is read and  processing	starts
			     over  with	 the first pattern in the AWK program.
			     If the end of the input data is reached, the  END
			     block(s), if any, are executed.

       nextfile		     Stop processing the current input file.  The next
			     input record read comes from the next input file.
			     FILENAME  and ARGIND are updated, FNR is reset to
			     1, and processing starts over with the first pat‐
			     tern  in the AWK program. If the end of the input
			     data is reached, the END block(s),	 if  any,  are

       print		     Prints  the current record.  The output record is
			     terminated with the value of the ORS variable.

       print expr-list	     Prints expressions.  Each expression is separated
			     by	 the  value  of	 the OFS variable.  The output
			     record is terminated with the value  of  the  ORS

       print expr-list >file Prints  expressions  on file.  Each expression is
			     separated by the value of the OFS variable.   The
			     output record is terminated with the value of the
			     ORS variable.

       printf fmt, expr-list Format and print.

       printf fmt, expr-list >file
			     Format and print on file.

       system(cmd-line)	     Execute the command cmd-line, and return the exit
			     status.   (This may not be available on non-POSIX

       fflush([file])	     Flush any buffers associated with the open output
			     file  or  pipe  file.   If	 file is missing, then
			     standard output is flushed.  If file is the  null
			     string, then all open output files and pipes have
			     their buffers flushed.

       Additional output redirections are allowed for print and printf.

       print ... >> file
	      appends output to the file.

       print ... | command
	      writes on a pipe.

       print ... |& command
	      sends data to a co-process.

       The getline command returns 0 on end of file and -1 on an error.	  Upon
       an error, ERRNO contains a string describing the problem.

       NOTE: If using a pipe or co-process to getline, or from print or printf
       within a loop, you must use close() to create new instances of the com‐
       mand.  AWK does not automatically close pipes or co-processes when they
       return EOF.

   The printf Statement
       The AWK versions of the printf statement and  sprintf()	function  (see
       below) accept the following conversion specification formats:

       %c      An ASCII character.  If the argument used for %c is numeric, it
	       is treated as a character and printed.  Otherwise, the argument
	       is assumed to be a string, and the only first character of that
	       string is printed.

       %d, %i  A decimal number (the integer part).

       %e ,  %E
	       A floating point number of the form [-]d.dddddde[+-]dd.	The %E
	       format uses E instead of e.

       %f      A floating point number of the form [-]ddd.dddddd.

       %g ,  %G
	       Use %e or %f conversion, whichever is shorter, with nonsignifi‐
	       cant zeros suppressed.  The %G format uses %E instead of %e.

       %o      An unsigned octal number (also an integer).

       %u      An unsigned decimal number (again, an integer).

       %s      A character string.

       %x ,  %X
	       An unsigned hexadecimal number (an  integer).   The  %X	format
	       uses ABCDEF instead of abcdef.

       %%      A single % character; no argument is converted.

       NOTE: When using the integer format-control letters for values that are
       outside the range of a C long integer, gawk switches to the  %g	format
       specifier.  If  --lint is provided on the command line gawk warns about
       this.  Other versions of awk may print invalid values or	 do  something
       else entirely.

       Optional,  additional  parameters may lie between the % and the control

       count$ Use the count'th argument at this point in the formatting.  This
	      is  called  a positional specifier and is intended primarily for
	      use in translated versions of format strings, not in the	origi‐
	      nal text of an AWK program.  It is a gawk extension.

       -      The expression should be left-justified within its field.

       space  For  numeric  conversions,  prefix positive values with a space,
	      and negative values with a minus sign.

       +      The plus sign, used before the width modifier (see below),  says
	      to  always  supply  a  sign for numeric conversions, even if the
	      data to be formatted is positive.	 The  +	 overrides  the	 space

       #      Use  an  “alternate  form” for certain control letters.  For %o,
	      supply a leading zero.  For %x, and %X, supply a leading	0x  or
	      0X  for a nonzero result.	 For %e, %E, and %f, the result always
	      contains a decimal point.	 For %g, and %G,  trailing  zeros  are
	      not removed from the result.

       0      A	 leading 0 (zero) acts as a flag, that indicates output should
	      be padded with zeroes instead of spaces.	This applies  even  to
	      non-numeric  output  formats.  This flag only has an effect when
	      the field width is wider than the value to be printed.

       width  The field should be padded to this width.	 The field is normally
	      padded  with  spaces.  If the 0 flag has been used, it is padded
	      with zeroes.

       .prec  A number that specifies the precision to use when printing.  For
	      the  %e, %E, and %f formats, this specifies the number of digits
	      you want printed to the right of the decimal point.  For the %g,
	      and  %G  formats, it specifies the maximum number of significant
	      digits.  For the %d, %o, %i, %u, %x, and %X formats,  it	speci‐
	      fies  the	 minimum number of digits to print.  For %s, it speci‐
	      fies the maximum number  of  characters  from  the  string  that
	      should be printed.

       The dynamic width and prec capabilities of the ANSI C printf() routines
       are supported.  A * in place of either the width or prec specifications
       causes  their  values  to  be taken from the argument list to printf or
       sprintf().  To use a positional specifier with a dynamic width or  pre‐
       cision,	supply the count$ after the * in the format string.  For exam‐
       ple, "%3$*2$.*1$s".

   Special File Names
       When doing I/O redirection from either print or printf into a file,  or
       via  getline  from  a  file,  gawk recognizes certain special filenames
       internally.  These filenames allow  access  to  open  file  descriptors
       inherited  from	gawk's parent process (usually the shell).  These file
       names may also be used on the command line to  name  data  files.   The
       filenames are:

       /dev/stdin  The standard input.

       /dev/stdout The standard output.

       /dev/stderr The standard error output.

       /dev/fd/n   The file associated with the open file descriptor n.

       These are particularly useful for error messages.  For example:

	      print "You blew it!" > "/dev/stderr"

       whereas you would otherwise have to use

	      print "You blew it!" | "cat 1>&2"

       The  following  special	filenames  may	be used with the |& co-process
       operator for creating TCP/IP network connections.

       /inet/tcp/lport/rhost/rport  File for TCP/IP connection on  local  port
				    lport  to remote host rhost on remote port
				    rport.  Use a port of 0 to have the system
				    pick a port.

       /inet/udp/lport/rhost/rport  Similar, but use UDP/IP instead of TCP/IP.

       /inet/raw/lport/rhost/rport  Reserved for future use.

       Other special filenames provide access to information about the running
       gawk process.  These filenames are  now	obsolete.   Use	 the  PROCINFO
       array to obtain the information they provide.  The filenames are:

       /dev/pid	   Reading  this  file	returns	 the process ID of the current
		   process, in decimal, terminated with a newline.

       /dev/ppid   Reading this file returns the parent process ID of the cur‐
		   rent process, in decimal, terminated with a newline.

       /dev/pgrpid Reading  this file returns the process group ID of the cur‐
		   rent process, in decimal, terminated with a newline.

       /dev/user   Reading this file returns a single record terminated with a
		   newline.   The fields are separated with spaces.  $1 is the
		   value of the getuid(2) system call, $2 is the value of  the
		   geteuid(2)  system  call,  $3 is the value of the getgid(2)
		   system call, and $4 is the value of the  getegid(2)	system
		   call.   If  there  are  any additional fields, they are the
		   group IDs returned by getgroups(2).	 Multiple  groups  may
		   not be supported on all systems.

   Numeric Functions
       AWK has the following built-in arithmetic functions:

       atan2(y, x)   Returns the arctangent of y/x in radians.

       cos(expr)     Returns the cosine of expr, which is in radians.

       exp(expr)     The exponential function.

       int(expr)     Truncates to integer.

       log(expr)     The natural logarithm function.

       rand()	     Returns a random number N, between 0 and 1, such that 0 ≤
		     N < 1.

       sin(expr)     Returns the sine of expr, which is in radians.

       sqrt(expr)    The square root function.

       srand([expr]) Uses expr as a new seed for the random number  generator.
		     If	 no  expr  is  provided, the time of day is used.  The
		     return value is the previous seed for the	random	number

   String Functions
       Gawk has the following built-in string functions:

       asort(s [, d])	       Returns	the  number  of elements in the source
			       array s.	 The contents of s  are	 sorted	 using
			       gawk's  normal  rules for comparing values, and
			       the indexes of  the  sorted  values  of	s  are
			       replaced with sequential integers starting with
			       1. If the optional destination array d is spec‐
			       ified,  then  s is first duplicated into d, and
			       then d is sorted, leaving the  indexes  of  the
			       source array s unchanged.

       asorti(s [, d])	       Returns	the  number  of elements in the source
			       array s.	 The behavior is the same as  that  of
			       asort(), except that the array indices are used
			       for sorting, not the array values.  When	 done,
			       the  array is indexed numerically, and the val‐
			       ues are those of	 the  original	indices.   The
			       original values are lost; thus provide a second
			       array if you wish to preserve the original.

       gensub(r, s, h [, t])   Search the target string t for matches  of  the
			       regular	expression r.  If h is a string begin‐
			       ning with g or G, then replace all matches of r
			       with  s.	  Otherwise,  h is a number indicating
			       which match of r to replace.  If t is not  sup‐
			       plied, $0 is used instead.  Within the replace‐
			       ment text s, the sequence  \n,  where  n	 is  a
			       digit from 1 to 9, may be used to indicate just
			       the text that matched  the  n'th	 parenthesized
			       subexpression.	The sequence \0 represents the
			       entire matched text, as does the	 character  &.
			       Unlike sub() and gsub(), the modified string is
			       returned as the result of the function, and the
			       original target string is not changed.

       gsub(r, s [, t])	       For each substring matching the regular expres‐
			       sion r in the string t, substitute  the	string
			       s,  and return the number of substitutions.  If
			       t is  not  supplied,  use  $0.	An  &  in  the
			       replacement text is replaced with the text that
			       was actually matched.  Use \& to get a  literal
			       &.   (This  must	 be  typed as "\\&"; see GAWK:
			       Effective AWK Programming for a fuller  discus‐
			       sion  of	 the  rules for &'s and backslashes in
			       the replacement text of sub(), gsub(), and gen‐

       index(s, t)	       Returns the index of the string t in the string
			       s, or 0 if t is	not  present.	(This  implies
			       that character indices start at one.)

       length([s])	       Returns	the  length  of	 the  string s, or the
			       length of $0 if s is not supplied.

       match(s, r [, a])       Returns the position in	s  where  the  regular
			       expression  r occurs, or 0 if r is not present,
			       and sets the  values  of	 RSTART	 and  RLENGTH.
			       Note that the argument order is the same as for
			       the ~ operator: str ~ re.  If array a  is  pro‐
			       vided, a is cleared and then elements 1 through
			       n are filled with the portions of s that	 match
			       the  corresponding  parenthesized subexpression
			       in r.  The 0'th element of a contains the  por‐
			       tion of s matched by the entire regular expres‐
			       sion r.	Subscripts  a[n,  "start"],  and  a[n,
			       "length"]  provide  the	starting  index in the
			       string and length respectively, of each	match‐
			       ing substring.

       split(s, a [, r])       Splits  the  string  s  into the array a on the
			       regular expression r, and returns the number of
			       fields.	 If  r is omitted, FS is used instead.
			       The  array  a  is  cleared  first.    Splitting
			       behaves	 identically   to   field   splitting,
			       described above.

       sprintf(fmt, expr-list) Prints expr-list according to fmt, and  returns
			       the resulting string.

       strtonum(str)	       Examines	 str,  and  returns its numeric value.
			       If str begins  with  a  leading	0,  strtonum()
			       assumes	that  str  is an octal number.	If str
			       begins with a  leading  0x  or  0X,  strtonum()
			       assumes that str is a hexadecimal number.

       sub(r, s [, t])	       Just  like  gsub(), but only the first matching
			       substring is replaced.

       substr(s, i [, n])      Returns the at most n-character substring of  s
			       starting	 at i.	If n is omitted, the rest of s
			       is used.

       tolower(str)	       Returns a copy of the string str, with all  the
			       upper-case  characters  in  str	translated  to
			       their  corresponding  lower-case	 counterparts.
			       Non-alphabetic characters are left unchanged.

       toupper(str)	       Returns	a copy of the string str, with all the
			       lower-case  characters  in  str	translated  to
			       their  corresponding  upper-case	 counterparts.
			       Non-alphabetic characters are left unchanged.

   Time Functions
       Since one of the primary uses of AWK programs is processing  log	 files
       that  contain time stamp information, gawk provides the following func‐
       tions for obtaining time stamps and formatting them.

		 Turns datespec into a time stamp of the same form as returned
		 by  systime().	  The datespec is a string of the form YYYY MM
		 DD HH MM SS[ DST].  The contents of the  string  are  six  or
		 seven numbers representing respectively the full year includ‐
		 ing century, the month from 1 to 12, the  day	of  the	 month
		 from  1  to  31, the hour of the day from 0 to 23, the minute
		 from 0 to 59, and the second from 0 to 60,  and  an  optional
		 daylight  saving  flag.  The values of these numbers need not
		 be within the ranges specified; for example, an  hour	of  -1
		 means 1 hour before midnight.	The origin-zero Gregorian cal‐
		 endar is assumed, with year 0 preceding year 1	 and  year  -1
		 preceding  year  0.   The  time is assumed to be in the local
		 timezone.  If the daylight saving flag is positive, the  time
		 is  assumed  to be daylight saving time; if zero, the time is
		 assumed to be standard time; and if negative  (the  default),
		 mktime()  attempts  to determine whether daylight saving time
		 is in effect for the specified time.  If  datespec  does  not
		 contain  enough  elements  or if the resulting time is out of
		 range, mktime() returns -1.

       strftime([format [, timestamp]])
		 Formats timestamp according to the specification  in  format.
		 The  timestamp should be of the same form as returned by sys‐
		 time().  If timestamp is missing, the current time of day  is
		 used.	 If  format is missing, a default format equivalent to
		 the output of date(1) is used.	 See the specification for the
		 strftime() function in ANSI C for the format conversions that
		 are guaranteed to be available.  A public-domain  version  of
		 strftime(3)  and  a  man  page for it come with gawk; if that
		 version was used to build gawk, then all of  the  conversions
		 described in that man page are available to gawk.

       systime() Returns  the  current	time  of  day as the number of seconds
		 since the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).

   Bit Manipulations Functions
       Starting with version 3.1 of gawk, the following bit manipulation func‐
       tions are available.  They work by converting double-precision floating
       point values to unsigned long integers, doing the operation,  and  then
       converting the result back to floating point.  The functions are:

       and(v1, v2)	   Return the bitwise AND of the values provided by v1
			   and v2.

       compl(val)	   Return the bitwise complement of val.

       lshift(val, count)  Return the value of	val,  shifted  left  by	 count

       or(v1, v2)	   Return  the bitwise OR of the values provided by v1
			   and v2.

       rshift(val, count)  Return the value of val,  shifted  right  by	 count

       xor(v1, v2)	   Return the bitwise XOR of the values provided by v1
			   and v2.

   Internationalization Functions
       Starting with version 3.1 of gawk, the following functions may be  used
       from  within your AWK program for translating strings at run-time.  For
       full details, see GAWK: Effective AWK Programming.

       bindtextdomain(directory [, domain])
	      Specifies the directory where gawk looks for the .mo  files,  in
	      case they will not or cannot be placed in the ``standard'' loca‐
	      tions (e.g., during testing).  It returns	 the  directory	 where
	      domain is ``bound.''
	      The  default domain is the value of TEXTDOMAIN.  If directory is
	      the null string (""), then bindtextdomain() returns the  current
	      binding for the given domain.

       dcgettext(string [, domain [, category]])
	      Returns  the  translation	 of  string  in text domain domain for
	      locale category category.	 The default value for domain  is  the
	      current  value of TEXTDOMAIN.  The default value for category is
	      If you supply a value for category, it must be a string equal to
	      one  of the known locale categories described in GAWK: Effective
	      AWK Programming.	You must  also	supply	a  text	 domain.   Use
	      TEXTDOMAIN if you want to use the current domain.

       dcngettext(string1 , string2 , number [, domain [, category]])
	      Returns  the  plural  form used for number of the translation of
	      string1 and string2 in text domain domain	 for  locale  category
	      category.	  The default value for domain is the current value of
	      TEXTDOMAIN.  The default value for category is "LC_MESSAGES".
	      If you supply a value for category, it must be a string equal to
	      one  of the known locale categories described in GAWK: Effective
	      AWK Programming.	You must  also	supply	a  text	 domain.   Use
	      TEXTDOMAIN if you want to use the current domain.

       Functions in AWK are defined as follows:

	      function name(parameter list) { statements }

       Functions  are executed when they are called from within expressions in
       either patterns or actions.  Actual parameters supplied in the function
       call  are  used	to  instantiate	 the formal parameters declared in the
       function.  Arrays are passed by reference, other variables  are	passed
       by value.

       Since  functions were not originally part of the AWK language, the pro‐
       vision for local variables is rather clumsy: They are declared as extra
       parameters  in the parameter list.  The convention is to separate local
       variables from real parameters by extra spaces in the  parameter	 list.
       For example:

	      function	f(p, q,	    a, b)   # a and b are local

	      /abc/	{ ... ; f(1, 2) ; ... }

       The left parenthesis in a function call is required to immediately fol‐
       low the function name, without any intervening white space.  This is to
       avoid  a	 syntactic  ambiguity  with  the concatenation operator.  This
       restriction does not apply to the built-in functions listed above.

       Functions may call each other and may be recursive.   Function  parame‐
       ters used as local variables are initialized to the null string and the
       number zero upon function invocation.

       Use return expr to return a value from a function.  The return value is
       undefined if no value is provided, or if the function returns by “fall‐
       ing off” the end.

       If --lint has been provided, gawk warns about calls to undefined	 func‐
       tions  at  parse	 time,	instead	 of at run time.  Calling an undefined
       function at run time is a fatal error.

       The word func may be used in place of function.

       Beginning with version 3.1 of gawk, you can dynamically add new	built-
       in  functions  to  the  running gawk interpreter.  The full details are
       beyond the scope of this manual page; see GAWK: Effective AWK  Program‐
       ming for the details.

       extension(object, function)
	       Dynamically  link  the  shared object file named by object, and
	       invoke function in  that	 object,  to  perform  initialization.
	       These  should  both  be provided as strings.  Returns the value
	       returned by function.

       This function is provided and documented in GAWK:  Effective  AWK  Pro‐
       gramming,  but everything about this feature is likely to change in the
       next release.  We STRONGLY recommend that you do not use	 this  feature
       for anything that you aren't willing to redo.

       pgawk  accepts  two  signals.   SIGUSR1 causes it to dump a profile and
       function call stack to the profile file, which is  either  awkprof.out,
       or  whatever file was named with the --profile option.  It then contin‐
       ues to run.  SIGHUP causes it to dump the  profile  and	function  call
       stack and then exit.

       Print and sort the login names of all users:

	    BEGIN     { FS = ":" }
		 { print $1 | "sort" }

       Count lines in a file:

		 { nlines++ }
	    END	 { print nlines }

       Precede each line by its number in the file:

	    { print FNR, $0 }

       Concatenate and line number (a variation on a theme):

	    { print NR, $0 }
       Run an external command for particular lines of data:

	    tail -f access_log |
	    awk '/myhome.html/ { system("nmap " $1 ">> logdir/myhome.html") }'

       String constants are sequences of characters enclosed in double quotes.
       In non-English speaking environments, it is possible to mark strings in
       the  AWK	 program  as  requiring translation to the native natural lan‐
       guage. Such strings are marked in the AWK program with a leading under‐
       score (“_”).  For example,

	      gawk 'BEGIN { print "hello, world" }'

       always prints hello, world.  But,

	      gawk 'BEGIN { print _"hello, world" }'

       might print bonjour, monde in France.

       There are several steps involved in producing and running a localizable
       AWK program.

       1.  Add a BEGIN action to assign a value to the TEXTDOMAIN variable  to
	   set the text domain to a name associated with your program.

		BEGIN { TEXTDOMAIN = "myprog" }

	   This allows gawk to find the .mo file associated with your program.
	   Without this step, gawk uses the messages text domain, which likely
	   does not contain translations for your program.

       2.  Mark	 all  strings  that  should  be translated with leading under‐

       3.  If necessary, use the dcgettext() and/or bindtextdomain() functions
	   in your program, as appropriate.

       4.  Run	gawk --gen-po -f myprog.awk > myprog.po to generate a .po file
	   for your program.

       5.  Provide appropriate translations, and build and  install  a	corre‐
	   sponding .mo file.

       The internationalization features are described in full detail in GAWK:
       Effective AWK Programming.

       A primary goal for gawk is compatibility with the  POSIX	 standard,  as
       well  as with the latest version of UNIX awk.  To this end, gawk incor‐
       porates the following user visible features which are not described  in
       the AWK book, but are part of the Bell Laboratories version of awk, and
       are in the POSIX standard.

       The book indicates that command line variable assignment	 happens  when
       awk  would  otherwise  open  the argument as a file, which is after the
       BEGIN block is executed.	 However,  in  earlier	implementations,  when
       such an assignment appeared before any file names, the assignment would
       happen before the BEGIN block was run.  Applications came to depend  on
       this  “feature.”	  When awk was changed to match its documentation, the
       -v option for assigning variables before program execution was added to
       accommodate  applications  that	depended upon the old behavior.	 (This
       feature was agreed upon by both	the  Bell  Laboratories	 and  the  GNU

       The  -W	option	for implementation specific features is from the POSIX

       When processing arguments, gawk uses the special option “--” to	signal
       the end of arguments.  In compatibility mode, it warns about but other‐
       wise ignores undefined options.	In normal  operation,  such  arguments
       are passed on to the AWK program for it to process.

       The  AWK	 book  does not define the return value of srand().  The POSIX
       standard has it return the seed it was using, to allow keeping track of
       random  number  sequences.   Therefore srand() in gawk also returns its
       current seed.

       Other new features are: The use of multiple -f options (from MKS	 awk);
       the  ENVIRON array; the \a, and \v escape sequences (done originally in
       gawk and fed back into the Bell Laboratories  version);	the  tolower()
       and  toupper() built-in functions (from the Bell Laboratories version);
       and the ANSI C conversion specifications in printf (done first  in  the
       Bell Laboratories version).

       There are two features of historical AWK implementations that gawk sup‐
       ports.  First, it is possible to call the  length()  built-in  function
       not only with no argument, but even without parentheses!	 Thus,

	      a = length     # Holy Algol 60, Batman!

       is the same as either of

	      a = length()
	      a = length($0)

       This  feature is marked as “deprecated” in the POSIX standard, and gawk
       issues a warning about its use if --lint is specified  on  the  command

       The other feature is the use of either the continue or the break state‐
       ments outside the body of a while, for, or do  loop.   Traditional  AWK
       implementations	have  treated  such  usage  as	equivalent to the next
       statement.  Gawk supports this usage if --traditional has  been	speci‐

       Gawk  has  a  number of extensions to POSIX awk.	 They are described in
       this section.  All the extensions described here	 can  be  disabled  by
       invoking gawk with the --traditional option.

       The following features of gawk are not available in POSIX awk.

       · No  path  search  is  performed  for  files  named via the -f option.
	 Therefore the AWKPATH environment variable is not special.

       · The \x escape sequence.  (Disabled with --posix.)

       · The fflush() function.	 (Disabled with --posix.)

       · The ability to	 continue  lines  after	 ?   and  :.   (Disabled  with

       · Octal and hexadecimal constants in AWK programs.

       · The ARGIND, BINMODE, ERRNO, LINT, RT and TEXTDOMAIN variables are not

       · The IGNORECASE variable and its side-effects are not available.

       · The FIELDWIDTHS variable and fixed-width field splitting.

       · The PROCINFO array is not available.

       · The use of RS as a regular expression.

       · The special file names available for I/O redirection are  not	recog‐

       · The |& operator for creating co-processes.

       · The  ability to split out individual characters using the null string
	 as the value of FS, and as the third argument to split().

       · The optional second argument to the close() function.

       · The optional third argument to the match() function.

       · The ability to use positional specifiers with printf and sprintf().

       · The use of delete array to delete the entire contents of an array.

       · The use of nextfile to abandon processing of the current input file.

       · The and(), asort(), asorti(), bindtextdomain(), compl(), dcgettext(),
	 dcngettext(),	gensub(),  lshift(),  mktime(),	 or(), rshift(), strf‐
	 time(), strtonum(), systime() and xor() functions.

       · Localizable strings.

       · Adding new built-in functions dynamically with the extension()	 func‐

       The  AWK book does not define the return value of the close() function.
       Gawk's close() returns the value from  fclose(3),  or  pclose(3),  when
       closing an output file or pipe, respectively.  It returns the process's
       exit status when closing an input pipe.	The return value is -1 if  the
       named file, pipe or co-process was not opened with a redirection.

       When  gawk is invoked with the --traditional option, if the fs argument
       to the -F option is “t”, then FS is set to  the	tab  character.	  Note
       that  typing  gawk -F\t ...  simply causes the shell to quote the “t,”,
       and does not pass “\t” to the -F option.	 Since this is a  rather  ugly
       special	case, it is not the default behavior.  This behavior also does
       not occur if --posix has been specified.	 To really get a tab character
       as  the	field  separator, it is best to use single quotes: gawk -F'\t'

       The AWKPATH environment variable can be	used  to  provide  a  list  of
       directories  that gawk searches when looking for files named via the -f
       and --file options.

       If POSIXLY_CORRECT exists in the environment, then gawk behaves exactly
       as  if  --posix	had been specified on the command line.	 If --lint has
       been specified, gawk issues a warning message to this effect.

       egrep(1), getpid(2),  getppid(2),  getpgrp(2),  getuid(2),  geteuid(2),
       getgid(2), getegid(2), getgroups(2)

       The  AWK Programming Language, Alfred V. Aho, Brian W. Kernighan, Peter
       J. Weinberger, Addison-Wesley, 1988.  ISBN 0-201-07981-X.

       GAWK: Effective AWK Programming, Edition 3.0,  published	 by  the  Free
       Software Foundation, 2001.

       The  -F option is not necessary given the command line variable assign‐
       ment feature; it remains only for backwards compatibility.

       Syntactically invalid single character programs tend  to	 overflow  the
       parse  stack, generating a rather unhelpful message.  Such programs are
       surprisingly difficult to diagnose in the completely general case,  and
       the effort to do so really is not worth it.

       The original version of UNIX awk was designed and implemented by Alfred
       Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories.	 Brian
       Kernighan continues to maintain and enhance it.

       Paul  Rubin  and	 Jay  Fenlason, of the Free Software Foundation, wrote
       gawk, to be compatible with the original version of awk distributed  in
       Seventh	Edition	 UNIX.	 John Woods contributed a number of bug fixes.
       David Trueman, with contributions from Arnold Robbins, made  gawk  com‐
       patible	with  the new version of UNIX awk.  Arnold Robbins is the cur‐
       rent maintainer.

       The initial DOS port was done  by  Conrad  Kwok	and  Scott  Garfinkle.
       Scott Deifik is the current DOS maintainer.  Pat Rankin did the port to
       VMS, and Michal Jaegermann did the port to the Atari ST.	 The  port  to
       OS/2  was done by Kai Uwe Rommel, with contributions and help from Dar‐
       rel Hankerson.  Fred Fish  supplied  support  for  the  Amiga,  Stephen
       Davies  provided	 the  Tandem  port, and Martin Brown provided the BeOS

       This man page documents gawk, version 3.1.3.

       If you find a  bug  in  gawk,  please  send  electronic	mail  to  bug-   Please  include your operating system and its revision,
       the version of gawk (from gawk --version), what C compiler you used  to
       compile	it,  and a test program and data that are as small as possible
       for reproducing the problem.

       Before sending a bug report, please do two things.  First, verify  that
       you  have  the latest version of gawk.  Many bugs (usually subtle ones)
       are fixed at each release, and if yours is out of date, the problem may
       already	have  been  solved.  Second, please read this man page and the
       reference manual carefully to be sure that what	you  think  is	a  bug
       really is, instead of just a quirk in the language.

       Whatever	 you do, do NOT post a bug report in comp.lang.awk.  While the
       gawk developers occasionally read this newsgroup, posting  bug  reports
       there  is  an  unreliable  way to report bugs.  Instead, please use the
       electronic mail addresses given above.

       Brian Kernighan of Bell Laboratories provided valuable assistance  dur‐
       ing testing and debugging.  We thank him.

       Copyright © 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
       2001, 2002, 2003 Free Software Foundation, Inc.

       Permission is granted to make and distribute verbatim  copies  of  this
       manual  page  provided  the copyright notice and this permission notice
       are preserved on all copies.

       Permission is granted to copy and distribute modified versions of  this
       manual  page  under  the conditions for verbatim copying, provided that
       the entire resulting derived work is distributed under the terms	 of  a
       permission notice identical to this one.

       Permission  is granted to copy and distribute translations of this man‐
       ual page into another language, under the above conditions for modified
       versions,  except that this permission notice may be stated in a trans‐
       lation approved by the Foundation.

Free Software Foundation	 June 25 2003			       GAWK(1)

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