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GAWK(1)			       Utility Commands			       GAWK(1)

NAME
       gawk - pattern scanning and processing language

SYNOPSIS
       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 ...

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

DESCRIPTION
       Gawk  is	 the  GNU Project's implementation of the AWK programming lan‐
       guage.  It conforms to the definition of	 the  language	in  the	 POSIX
       1003.1  Standard.   This version in turn is based on the description in
       The AWK Programming Language, by Aho, Kernighan, and Weinberger.	  Gawk
       provides	 the  additional features found in the current version of UNIX
       awk and a number of GNU-specific extensions.

       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.

       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.

       Dgawk  is  an awk debugger. Instead of running the program directly, it
       loads the AWK source code and  then  prompts  for  debugging  commands.
       Unlike gawk and pgawk, dgawk only processes AWK program source provided
       with the -f option.  The debugger is documented in GAWK: Effective  AWK
       Programming.

OPTION FORMAT
       Gawk  options may be either traditional POSIX-style 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-specific features and for POSIX-mandated features.

       Gawk- specific options are typically used in long-option	 form.	 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.

       Additionally, each long option has a  corresponding  short  option,  so
       that  the option's functionality may be used from within #!  executable
       scripts.

OPTIONS
       Gawk accepts the following options.  Standard options are listed first,
       followed by options for gawk extensions, listed alphabetically by short
       option.

       -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.

       -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.

       -b
       --characters-as-bytes
	      Treat  all input data as single-byte characters. In other words,
	      don't pay any attention to the locale information when  attempt‐
	      ing  to  process	strings	 as multibyte characters.  The --posix
	      option overrides this one.

       -c
       --traditional
	      Run in compatibility mode.  In compatibility mode, gawk  behaves
	      identically to UNIX awk; none of the GNU-specific extensions are
	      recognized.  See GNU EXTENSIONS, below, for more information.

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

       -d[file]
       --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.)

       -e 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.

       -E file
       --exec file
	      Similar  to  -f,	however,  this	is option is the last one pro‐
	      cessed.  This should be used with #!  scripts, particularly  for
	      CGI applications, to avoid passing in options or source code (!)
	      on the command line from a URL.  This option  disables  command-
	      line variable assignments.

       -g
       --gen-pot
	      Scan  and parse the AWK program, and generate a GNU .pot (Porta‐
	      ble Object Template) 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 .pot files.

       -h
       --help 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.)

       -L [value]
       --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.)

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

       -N
       --use-lc-numeric
	      This forces gawk to use the  locale's  decimal  point  character
	      when  parsing  input data.  Although the POSIX standard requires
	      this behavior, and gawk does so when --posix is in  effect,  the
	      default  is  to  follow traditional behavior and use a period as
	      the decimal point, even in locales where the period is  not  the
	      decimal  point  character.   This	 option	 overrides the default
	      behavior, without the full draconian strictness of  the  --posix
	      option.

       -O
       --optimize
	      Enable  optimizations  upon  the	internal representation of the
	      program.	Currently, this includes just simple constant-folding.
	      The  gawk	 maintainer hopes to add additional optimizations over
	      time.

       -p[prof_file]
       --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.

       -P
       --posix
	      This turns on compatibility mode, with the following  additional
	      restrictions:

	      · \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.

       -r
       --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.  They are enabled by default, but this option remains for
	      use with --traditional.

       -R
       --command file
	      Dgawk only.  Read stored debugger commands from file.

       -S
       --sandbox
	      Runs  gawk  in  sandbox  mode,  disabling the system() function,
	      input redirection with getline, output  redirection  with	 print
	      and  printf,  and loading dynamic extensions.  Command execution
	      (through pipelines) is also disabled.  This effectively blocks a
	      script  from  accessing  local  resources	 (except for the files
	      specified on the command line).

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

       -V
       --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 pro‐
	      vides 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.

AWK PROGRAM EXECUTION
       An  AWK program consists of a sequence of pattern-action statements and
       optional function definitions.

	      @include "filename" 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
       programs.

       In addition, lines beginning with @include may be used to include other
       source files into your program, making library use even easier.

       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 (up to ARGV[ARGC]).   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 input file, if a BEGINFILE  rule  exists,  gawk	 executes  the
       associated  code before processing the contents of the file. Similarly,
       gawk executes the code associated with  ENDFILE	after  processing  the
       file.

       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).

   Command Line Directories
       According  to  POSIX,  files named on the awk command line must be text
       files.  The behavior is ``undefined'' if they are not.	Most  versions
       of awk treat a directory on the command line as a fatal error.

       Starting with version 4.0 of gawk, a directory on the command line pro‐
       duces a warning, but is otherwise skipped.  If either of the --posix or
       --traditional  options is given, then gawk reverts to treating directo‐
       ries on the command line as a fatal error.

VARIABLES, RECORDS AND FIELDS
       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  are	 described  as
       needed and summarized below.

   Records
       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.

   Fields
       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 section POSIX COMPATIBILITY,
       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 or FPAT overrides the use of FIELDWIDTHS.

       Similarly, if the FPAT variable is set to a string representing a regu‐
       lar expression, each field is made up of text that matches that regular
       expression. In this case, the regular expression describes  the	fields
       themselves, instead of the text that separates the fields.  Assigning a
       new value to FS or FIELDWIDTHS overrides the use of FPAT.

       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
       record.

       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  whitespace  separated  list  of field widths.  When set,
		   gawk parses the input into fields of fixed  width,  instead
		   of  using the value of the FS variable as the field separa‐
		   tor.	 See Fields, above.

       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.

       FPAT	   A  regular expression describing the contents of the fields
		   in a record.	 When set, gawk parses the input into  fields,
		   where  the  fields match the regular expression, instead of
		   using the value of the FS variable as the field  separator.
		   See Fields, above.

       FS	   The input field separator, a space by default.  See Fields,
		   above.

       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 and FPAT, record separating with
		   RS, regular expression matching with ~ and !~, and the gen‐
		   sub(),  gsub(),  index(), match(), patsplit(), split(), and
		   sub() built-in functions all ignore case when doing regular
		   expression  operations.   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.

       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
		   available:

		   PROCINFO["egid"]    the  value  of  the  getegid(2)	system
				       call.

		   PROCINFO["strftime"]
				       The  default  time  format  string  for
				       strftime().

		   PROCINFO["euid"]    the  value  of  the  geteuid(2)	system
				       call.

		   PROCINFO["FS"]      "FS" if field splitting with FS	is  in
				       effect,	"FPAT" if field splitting with
				       FPAT is in effect, or "FIELDWIDTHS"  if
				       field  splitting with FIELDWIDTHS is in
				       effect.

		   PROCINFO["gid"]     the value of the getgid(2) system call.

		   PROCINFO["pgrpid"]  the process group  ID  of  the  current
				       process.

		   PROCINFO["pid"]     the process ID of the current process.

		   PROCINFO["ppid"]    the  parent  process  ID of the current
				       process.

		   PROCINFO["uid"]     the value of the getuid(2) system call.

		   PROCINFO["sorted_in"]
				       If this	element	 exists	 in  PROCINFO,
				       then  its  value	 controls the order in
				       which array elements are	 traversed  in
				       for   loops.    Supported   values  are
				       "@ind_str_asc",	       "@ind_num_asc",
				       "@val_type_asc",	       "@val_str_asc",
				       "@val_num_asc",	      "@ind_str_desc",
				       "@ind_num_desc",	     "@val_type_desc",
				       "@val_str_desc",	 "@val_num_desc",  and
				       "@unsorted".  The value can also be the
				       name of any comparison function defined
				       as follows:

			  function cmp_func(i1, v1, i2, v2)

		   where i1 and i2 are the indices, and v1 and v2 are the cor‐
		   responding values of the two elements being	compared.   It
		   should return a number less than, equal to, or greater than
		   0, depending on how the elements of the  array  are	to  be
		   ordered.

		   PROCINFO["version"]
			  the version of gawk.

       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
		   RS.

       RSTART	   The	index  of the first character matched by match(); 0 if
		   no match.  (This implies that character  indices  start  at
		   one.)

       RLENGTH	   The	length	of  the	 string	 matched  by match(); -1 if no
		   match.

       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
       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 to test 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.

       gawk  supports  true  multidimensional arrays. It does not require that
       such arrays be ``rectangular'' as in C or C++.  For example:
	      a[1] = 5
	      a[2][1] = 6
	      a[2][2] = 7

   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".

       NOTE:  When  operating  in POSIX mode (such as with the --posix command
       line option), beware that locale settings may interfere	with  the  way
       decimal	numbers	 are treated: the decimal separator of the numbers you
       are feeding to gawk must conform to what your locale would  expect,  be
       it a comma (,) or a period (.).

       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 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() or patsplit() 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
       You may use C-style octal and hexadecimal 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 (like "value").  Within strings, certain escape sequences
       are recognized, 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/.

PATTERNS AND ACTIONS
       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 comma, {, ?, :, &&, 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 is 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.

   Patterns
       AWK patterns may be one of the following:

	      BEGIN
	      END
	      BEGINFILE
	      ENDFILE
	      /regular expression/
	      relational expression
	      pattern && 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.

       BEGINFILE and ENDFILE are additional special patterns whose bodies  are
       executed	 before	 reading  the  first record of each command line input
       file and after reading the last record of each file.  Inside the BEGIN‐
       FILE  rule,  the	 value	of  ERRNO will be the empty string if the file
       could be opened successfully.  Otherwise, there is  some	 problem  with
       the  file  and  the code should use nextfile to skip it. If that is not
       done, gawk produces its usual fatal error  for  files  that  cannot  be
       opened.

       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
       below.

       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
       evaluation.

       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
       evaluated.

       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}
       r{n,}
       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.

       \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.

       \s	  matches any whitespace character.

       \S	  matches any nonwhitespace character.

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

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

       \`	  matches the empty  string  at	 the  beginning	 of  a	buffer
		  (string).

       \'	  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 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:]  Lowercase alphabetic characters.

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

       [: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:]  Uppercase 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, no matter what it is.

       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 “`” 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, \<, \>, \s, \S, \w, \W, \`, and \' operators	 are  specific
       to  gawk;  they	are  extensions based on facilities in the GNU regular
       expression libraries.

       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.

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

       --traditional
	      Traditional Unix awk regular expressions are matched.   The  GNU
	      operators	 are  not  special,  and  interval expressions are not
	      available.  Characters described by octal and hexadecimal escape
	      sequences	 are treated literally, even if they represent regular
	      expression metacharacters.

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

   Actions
       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.

   Operators
       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.

       |   |&	   Piped I/O for getline, print, and printf.

       < > <= >= != ==
		   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
	      break
	      continue
	      delete array[index]
	      delete array
	      exit [ expression ]
	      { statements }
	      switch (expression) {
	      case value|regex : statement
	      ...
	      [ default: statement ]
	      }

   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.	(command can also be a
			     socket.  See the subsection Special  File	Names,
			     below.)

       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
			     executed.

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

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

       print expr-list >file Print  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.	  See  The  printf  Statement,
			     below.

       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
			     systems.)

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

       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 or socket.  (See also the subsection
	      Special File Names, below.)

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

       NOTE: Failure in opening a two-way socket will result  in  a  non-fatal
       error  being  returned  to  the	calling function. If using a pipe, co-
       process, or socket to getline, or from print or printf within  a	 loop,
       you  must use close() to create new instances of the command or socket.
       AWK does not automatically close pipes, sockets, 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      A single 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, %F  A floating point number of the form [-]ddd.dddddd.  If the sys‐
	       tem  library supports it, %F is available as well. This is like
	       %f, but uses capital letters for special	 “not  a  number”  and
	       “infinity” values. If %F is not available, gawk uses %f.

       %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
       letter:

       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
	      modifier.

       #      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, %f 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  only  to
	      the  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,  %f	 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 sig‐
	      nificant digits.	For the %d, %i, %o, %u, %x, and %X formats, it
	      specifies	 the  minimum  number  of digits to print.  For %s, it
	      specifies 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
       /inet4/tcp/lport/rhost/rport
       /inet6/tcp/lport/rhost/rport
	      Files for a 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.  Use /inet4 to force an IPv4 connection, and /inet6
	      to  force	 an  IPv6  connection.	 Plain	/inet  uses the system
	      default (most likely IPv4).

       /inet/udp/lport/rhost/rport
       /inet4/udp/lport/rhost/rport
       /inet6/udp/lport/rhost/rport
	      Similar, but use UDP/IP instead of TCP/IP.

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

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

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

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

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

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

       sqrt(expr)    The square root function.

       srand([expr]) Use expr as the new seed for the random number generator.
		     If no expr is provided, use the time of day.  The	return
		     value  is the previous seed for the random number genera‐
		     tor.

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

       asort(s [, d [, how] ]) Return the number of  elements  in  the	source
			       array  s.   Sort the contents of s using gawk's
			       normal rules for comparing values, and  replace
			       the indices of the sorted values s with sequen‐
			       tial integers starting with 1. If the  optional
			       destination  array  d  is specified, then first
			       duplicate s into d, and then  sort  d,  leaving
			       the  indices  of	 the source array s unchanged.
			       The optional string how controls the  direction
			       and  the comparison mode.  Valid values for how
			       are   any   of	the    strings	  valid	   for
			       PROCINFO["sorted_in"].  It can also be the name
			       of  a  user-defined  comparison	 function   as
			       described in PROCINFO["sorted_in"].

       asorti(s [, d [, how] ])
			       Return  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.
			       The  purpose  of the optional string how is the
			       same as described in asort() above.

       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,  use $0 instead.	Within the replacement
			       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 subex‐
			       pression.    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‐
			       sub().)

       index(s, t)	       Return  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])	       Return  the  length  of	the  string  s, or the
			       length of $0 if s is not supplied.  As  a  non-
			       standard	 extension,  with  an  array argument,
			       length() returns the number of elements in  the
			       array.

       match(s, r [, a])       Return  the  position  in  s  where the regular
			       expression r occurs, or 0 if r is not  present,
			       and set the values of RSTART and RLENGTH.  Note
			       that the argument order is the same as for  the
			       ~  operator: str ~ re.  If array a is provided,
			       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 portion of s
			       matched by the  entire  regular	expression  r.
			       Subscripts  a[n,	 "start"],  and a[n, "length"]
			       provide the starting index in  the  string  and
			       length  respectively,  of  each	matching  sub‐
			       string.

       patsplit(s, a [, r [, seps] ])
			       Split the string s into the  array  a  and  the
			       separators array seps on the regular expression
			       r, and return the number	 of  fields.   Element
			       values  are  the	 portions of s that matched r.
			       The value of  seps[i]  is  the  separator  that
			       appeared	 in front of a[i+1].  If r is omitted,
			       FPAT is used instead.  The arrays  a  and  seps
			       are  cleared  first.  Splitting behaves identi‐
			       cally to field splitting with  FPAT,  described
			       above.

       split(s, a [, r [, seps] ])
			       Split  the  string  s  into the array a and the
			       separators array seps on the regular expression
			       r,  and	return	the number of fields.  If r is
			       omitted, FS is used instead.  The arrays a  and
			       seps  are  cleared first.  seps[i] is the field
			       separator matched by r between a[i] and a[i+1].
			       If r is a single space, then leading whitespace
			       in s goes into the extra array element  seps[0]
			       and  trailing  whitespace  goes	into the extra
			       array element seps[n], where n  is  the	return
			       value  of  split(s,  a,	r,  seps).   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)	       Examine str, and return 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.   Otherwise,
			       decimal is assumed.

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

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

       tolower(str)	       Return a copy of the string str, with  all  the
			       uppercase characters in str translated to their
			       corresponding  lowercase	 counterparts.	  Non-
			       alphabetic characters are left unchanged.

       toupper(str)	       Return  a  copy of the string str, with all the
			       lowercase characters in str translated to their
			       corresponding   uppercase  counterparts.	  Non-
			       alphabetic characters are left unchanged.

       Gawk is multibyte aware.	 This means that index(),  length(),  substr()
       and match() all work in terms of characters, not bytes.

   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.

       mktime(datespec)
		 Turn  datespec into a time stamp of the same form as returned
		 by systime(), and return  the	result.	  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  respec‐
		 tively	 the  full year including 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, 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	 calendar is assumed, with year 0 pre‐
		 ceding 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[, utc-flag]]])
		 Format	 timestamp  according  to the specification in format.
		 If utc-flag is present	 and  is  non-zero  or	non-null,  the
		 result is in UTC, otherwise the result is in local time.  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.  The default format is avail‐
		 able in PROCINFO["strftime"].	See the specification for  the
		 strftime() function in ANSI C for the format conversions that
		 are guaranteed to be available.

       systime() Return 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
       Gawk  supplies  the following bit manipulation functions.  They work by
       converting double-precision floating point values  to  uintmax_t	 inte‐
       gers,  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
			   bits.

       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
			   bits.

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

   Type Function
       The following function is for use with multidimensional arrays.

       isarray(x)
	      Return true if x is an array, false otherwise.

   Internationalization Functions
       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])
	      Specify  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]])
	      Return 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
	      "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.

       dcngettext(string1 , string2 , number [, domain [, category]])
	      Return 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.

USER-DEFINED FUNCTIONS
       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 whitespace.  This avoids
       a syntactic ambiguity with the concatenation operator.	This  restric‐
       tion 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.

       As  a  gawk  extension, functions may be called indirectly. To do this,
       assign the name of the function to be called, as a string, to  a	 vari‐
       able.  Then use the variable as if it were the name of a function, pre‐
       fixed with an @ sign, like so:
	      function	myfunc()
	      {
		   print "myfunc called"
		   ...
	      }

	      {	   ...
		   the_func = "myfunc"
		   @the_func()	  # call through the_func to myfunc
		   ...
	      }

       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.

DYNAMICALLY LOADING NEW FUNCTIONS
       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 Programming 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.   Return  the	 value
	       returned by function.

       Using  this feature at the C level is not pretty, but it is unlikely to
       go away. Additional mechanisms may be added at some point.

SIGNALS
       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 pgawk to dump the profile and function call
       stack and then exit.

INTERNATIONALIZATION
       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 local natural language.
       Such  strings  are  marked in the AWK program with a leading underscore
       (“_”).  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‐
	   scores.

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

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

       5.  Provide  appropriate translations, and build and install the corre‐
	   sponding .mo files.

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

POSIX COMPATIBILITY
       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
       developers.)

       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).

HISTORICAL FEATURES
       There  is  one feature of historical AWK implementations that gawk sup‐
       ports: 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)

       Using  this  feature  is poor practice, and gawk issues a warning about
       its use if --lint is specified on the command line.

GNU EXTENSIONS
       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 or --posix options.

       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.

       · There is no facility for doing file inclusion (gawk's @include mecha‐
	 nism).

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

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

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

       · Octal and hexadecimal constants in AWK programs.

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

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

       · The FIELDWIDTHS variable and fixed-width field splitting.

       · The FPAT variable and field splitting based on field values.

       · 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‐
	 nized.

       · The |& operator for creating co-processes.

       · The BEGINFILE and ENDFILE special patterns are not available.

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

       · An optional fourth argument  to  split()  to  receive	the  separator
	 texts.

       · 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 ability to pass an array to length().

       · 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(),   patsplit(),
	 rshift(), strftime(), strtonum(), systime() and xor() functions.

       · Localizable strings.

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

       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'
       ....

ENVIRONMENT VARIABLES
       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.

       For socket communication, two special environment variables can be used
       to control the number of retries (GAWK_SOCK_RETRIES), and the  interval
       between retries (GAWK_MSEC_SLEEP).  The interval is in milliseconds. On
       systems that do not support usleep(3), the value is rounded  up	to  an
       integral number of seconds.

       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.

EXIT STATUS
       If  the	exit  statement is used with a value, then gawk exits with the
       numeric value given to it.

       Otherwise, if there were no problems during execution, gawk exits  with
       the value of the C constant EXIT_SUCCESS.  This is usually zero.

       If  an  error  occurs,  gawk  exits  with  the  value of the C constant
       EXIT_FAILURE.  This is usually one.

       If gawk exits because of a fatal error, the exit status is 2.  On  non-
       POSIX systems, this value may be mapped to EXIT_FAILURE.

VERSION INFORMATION
       This man page documents gawk, version 4.0.

AUTHORS
       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  maintains the port to MS-DOS using DJGPP.	 Eli Zaretskii
       maintains the port to MS-Windows using MinGW.  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
       Darrel  Hankerson.   Andreas  Buening now maintains the OS/2 port.  The
       late Fred Fish supplied support for the Amiga, and  Martin  Brown  pro‐
       vided the BeOS port.  Stephen Davies provided the original Tandem port,
       and Matthew Woehlke provided changes for Tandem's POSIX-compliant  sys‐
       tems.  Dave Pitts provided the port to z/OS.

       See the README file in the gawk distribution for up-to-date information
       about maintainers and which ports are currently supported.

BUG REPORTS
       If you find a  bug  in  gawk,  please  send  electronic	mail  to  bug-
       gawk@gnu.org.   Please  include your operating system and its revision,
       the version of gawk (from gawk --version), which 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 the  following  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 see if set‐
       ting the environment variable  LC_ALL  to  LC_ALL=C  causes  things  to
       behave  as  you	expect. If so, it's a locale issue, and may or may not
       really be a bug.	 Finally, 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.

       If you're using a GNU/Linux or BSD-based system, you may wish to submit
       a bug report to the vendor of  your  distribution.   That's  fine,  but
       please send a copy to the official email address as well, since there's
       no guarantee that the bug report will be forwarded to  the  gawk	 main‐
       tainer.

BUGS
       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.

SEE ALSO
       egrep(1),  getpid(2),  getppid(2),  getpgrp(2),	getuid(2), geteuid(2),
       getgid(2), getegid(2), getgroups(2), usleep(3)

       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 4.0, shipped with the gawk
       source.	The current version of this document is	 available  online  at
       http://www.gnu.org/software/gawk/manual.

EXAMPLES
       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") }'

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

COPYING PERMISSIONS
       Copyright © 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
       2001,  2002,  2003,  2004,  2005,  2007, 2009, 2010, 2011 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	  Nov 10 2011			       GAWK(1)
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