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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[=fatal]
	      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.

       -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

	      o	\x escape sequences are	not recognized.

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

	      o	You cannot continue lines after	?  and :.

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

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

	      o	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,	nor is
		   the asort() function.
		   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, e', or	e`.

       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.

       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 between 0 and 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.

       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.

       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.

		 Rurns 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
       "falling	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 }

       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.

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

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

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

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

       o Octal and hexadecimal constants in AWK	programs.

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

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

       o The FIELDWIDTHS variable and fixed-width field	splitting.

       o The PROCINFO array is not available.

       o The use of RS as a regular expression.

       o The  special  file names available for	I/O redirection	are not	recog-

       o The |&	operator for creating co-processes.

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

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

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

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

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

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

       o The and(), asort(), bindtextdomain(), compl(),	dcgettext(), gensub(),
	 lshift(), mktime(), or(), rshift(), strftime(), strtonum(), systime()
	 and xor() functions.

       o Localizable strings.

       o 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 3.1.0.

       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  (C)  1989,  1991,  1992, 1993, 1994, 1995, 1996, 1997, 1998,
       1999, 2001, 2002	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	  Apr 16 2002			       GAWK(1)


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