gawk

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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 ...

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,  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 extensions.

       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.

OPTION FORMAT
       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-
       specific 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.

OPTIONS
       Gawk accepts the following options, listed by frequency.

       -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  an  earlier
	      version  of  the Bell Laboratories research version of UNIX awk.
	      They are ignored by gawk, since gawk has no pre-defined  limits.

       -W compat
       -W traditional
       --compat
       --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
	      information.

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

       -W dump-variables[=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.)

       -W exec 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.

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

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

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

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

       -W posix
       --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.

       -W profile[=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.

       -W re-interval
       --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 use-lc-numeric
       --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.

       -W version
       --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.
	      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.
       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).
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  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
       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 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-
		   tor.
       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,
		   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, record separating with RS, regular
		   expression  matching	 with  ~  and  !~,  and	 the gensub(),
		   gsub(), index(), match(), split(), and sub() built-in func-
		   tions  all ignore case when doing regular expression opera-
		   tions.  NOTE: Array subscripting is not affected.  However,
		   the asort() and asorti() functions are affected.
		   Thus,  if IGNORECASE is not equal to zero, /aB/ matches all
		   of the strings "ab", "aB", "Ab", and "AB".  As with all AWK
		   variables,  the initial value of IGNORECASE is zero, so all
		   regular expression and string operations are normally case-
		   sensitive.  Under Unix, the full ISO 8859-1 Latin-1 charac-
		   ter set is used when ignoring case.	As of gawk 3.1.4,  the
		   case	 equivalencies	are fully locale-aware, based on the C
		   <ctype.h> facilities such as isalpha(), and toupper().
       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["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
				      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["version"]
				      The version of gawk.  This is  available
				      from version 3.1.4 and later.
       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.
   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".
       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 feed-
       ing  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() 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/.
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 ",", {, ?, :, &&, 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.
   Patterns
       AWK patterns may be one of the following:
	      BEGIN
	      END
	      /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.
       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.
		  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
		  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:]  Lower-case 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:]  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, 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, \<, \>, \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.	However, interval  expressions	are  not  sup-
	      ported.

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

       --traditional
	      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.

       --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 }

   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		     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
			     variable.

       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
			     systems.)

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

       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, 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      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, %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.

       NOTE: When using the integer format-control letters for values that are
       outside the range of a C long integer, gawk switches to the %0f	format
       specifier.  If  --lint is provided on the command line gawk warns about
       this.  Other versions of awk may print invalid values or	 do  something
       else entirely.

       Optional,  additional  parameters may lie between the % and the control
       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  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,  %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, %o, %i, %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  File for TCP/IP connection on  local  port
				    lport  to remote host rhost on remote port
				    rport.  Use a port of 0 to have the system
				    pick a port.

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

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

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

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

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

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

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

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


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

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

       exp(expr)     The exponential function.

       int(expr)     Truncates to integer.

       log(expr)     The natural logarithm function.

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

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

       sqrt(expr)    The square root function.

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

   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  indices  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 indices of the
			       source array s unchanged.

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

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

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

       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.  Starting
			       with version 3.1.5, as  a  non-standard	exten-
			       sion,  with an array argument, length() returns
			       the number of elements in the array.

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

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

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

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

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

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

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

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

       As of version 3.1.5, 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)
		 Turns datespec into a time stamp of the same form as returned
		 by  systime().	  The datespec is a string of the form YYYY MM
		 DD HH MM SS[ DST].  The contents of the  string  are  six  or
		 seven numbers representing respectively the full year includ-
		 ing century, the month from 1 to 12, the  day	of  the	 month
		 from  1  to  31, the hour of the day from 0 to 23, the minute
		 from 0 to 59, and the second from 0 to 60,  and  an  optional
		 daylight  saving  flag.  The values of these numbers need not
		 be within the ranges specified; for example, an  hour	of  -1
		 means 1 hour before midnight.	The origin-zero Gregorian cal-
		 endar is assumed, with year 0 preceding year 1	 and  year  -1
		 preceding  year  0.   The  time is assumed to be in the local
		 timezone.  If the daylight saving flag is positive, the  time
		 is  assumed  to be daylight saving time; if zero, the time is
		 assumed to be standard time; and if negative  (the  default),
		 mktime()  attempts  to determine whether daylight saving time
		 is in effect for the specified time.  If  datespec  does  not
		 contain  enough  elements  or if the resulting time is out of
		 range, mktime() returns -1.

       strftime([format [, timestamp[, utc-flag]]])
		 Formats 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.	 See the specification for the
		 strftime() function in ANSI C for the format conversions that
		 are guaranteed to be available.

       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 uintmax_t integers, doing the operation, and then con-
       verting 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.


   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
	      "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]])
	      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.

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 white space.  This
       avoids 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.

DYNAMICALLY LOADING NEW FUNCTIONS
       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 eventu-
       ally.   We STRONGLY recommend that you do not use this feature for any-
       thing that you aren't willing to redo.

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.

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") }'

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	 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-
	   scores.

       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 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.)

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

       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 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
       line.

       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-
       fied.

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.

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

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

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

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

       ? The 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(), rshift(), strf-
	 time(), 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'
       ....

       If gawk is configured with the --enable-switch option to the  configure
       command, then it accepts an additional control-flow statement:
	      switch (expression) {
	      case value|regex : statement
	      ...
	      [ default: statement ]
	      }

       If gawk is configured with the --disable-directories-fatal option, then
       it will silently skip directories named on the  command	line.	Other-
       wise, it will do so only if invoked with the --traditional option.

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.

       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.

SEE ALSO
       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 current version	of  this  document  is
       available online at http://www.gnu.org/software/gawk/manual.

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.

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 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.  Juan M. Guerrero now maintains  the  OS/2  port.	  Fred
       Fish supplied support for the Amiga, and Martin Brown provided the BeOS
       port.  Stephen Davies provided the original Tandem  port,  and  Matthew
       Woehlke provided changes for Tandem's POSIX-compliant systems.

VERSION INFORMATION
       This man page documents gawk, version 3.1.6.

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), 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 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 system 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 will be forwarded to the gawk main-
       tainer.

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 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	  Oct 19 2007			       GAWK(1)