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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 language.  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 Wein-
       berger.	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.  Arguments 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 abbreviation 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 predefined 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 attempting 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  pro-
	      gram  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 particu-
	      larly 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 intermix-
	      ing 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 pro-
	      grams used in shell scripts.

       -E file
       --exec file
	      Similar to -f, however, this is option is the last one processed.  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 (Portable Object Template)
	      format file on standard output with entries for all localizable strings in the pro-
	      gram.   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-portable 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 warnings 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 dra-
	      conian 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  addi-
	      tional 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" version  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:

	      o \x escape sequences are not recognized.

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

	      o You cannot continue lines after ?  and :.

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

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

       -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  com-
	      mand 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 Standards, these
	      options cause an immediate, successful exit.)

       --     Signal the end of options. This is useful to allow further  arguments  to  the  AWK
	      program  itself  to  start with a "-".  This provides 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 specified, 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 speci-
       fied via the -v option are performed.  Next, gawk compiles 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 assign-
       ment.  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 values to the variables AWK uses to control how input is broken into fields  and
       records.   It  is  also	useful for controlling state if multiple 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 pattern in the AWK  pro-
       gram.   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 produces a warning, but
       is otherwise skipped.  If either of the --posix or --traditional options  is  given,  then
       gawk reverts to treating directories 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 val-
       ues 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 simu-
       lated.  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 separating 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 newline character always acts as a field separator, in addition to
       whatever 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  sepa-
       rate  field.   Otherwise,  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 IGNORE-
       CASE (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 numbers, 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 regular 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.   How-
       ever,  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 recomputed, 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"
		   specify  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 mes-
		   sage.

       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., ENVIRON["HOME"] might be /home/arnold).  Changing  this  array
		   does  not  affect the environment seen by programs which gawk spawns via redi-
		   rection 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 separator.  See Fields, above.

       FILENAME    The name of the current input file.	If no files are specified 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 separa-
		   tor.  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 match-
		   ing	in  rules,  field  splitting with FS and FPAT, record separating with RS,
		   regular expression matching with ~ and !~, and the gensub(), 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 nor-
		   mally 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 follow-
		   ing 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 con-
				       trols 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 com-
				       parison function defined as follows:

			  function cmp_func(i1, v1, i2, v2)

		   where i1 and i2 are the indices, and v1 and v2 are the corresponding 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 char-
		   acter 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  localized  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 associative, i.e. indexed by string values.

       The special operator in may be used to test if an array has an index consisting of a  par-
       ticular 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 ``rec-
       tangular'' 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 context.  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	accomplished  using  str-
       tod(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 converted 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 con-
       verted 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 con-
       stants.	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 pat-
       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
       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 following 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 commit-
	    tee.)  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  expressions (e.g.,
       /[ \t\f\n\r\v]/ matches whitespace characters).

       In compatibility  mode,	the  characters  represented  by  octal  and  hexadecimal  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 statements 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 writ-
       ten in a single BEGIN block.  They are executed before any of the input	is  read.   Simi-
       larly,  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 BEGINFILE 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, otherwise 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 pattern1, 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 expression.   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 reg-
       ular expressions.

       Character  classes are a feature introduced in the POSIX standard.  A character class is a
       special notation for describing lists of characters that have a	specific  attribute,  but
       where  the actual characters themselves can vary from country to country and/or from char-
       acter 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 keyword denoting the class, and :].  The charac-
       ter 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 characters.)

       [:punct:]  Punctuation characters (characters that are not letter, digits, control charac-
		  ters, 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 characters, 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 repre-
       sented with more than one character, as well as several characters that are equivalent for
       collating,  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 element, 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
	      expression 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 currently 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 expres-
       sions.

       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 reg-
	      ular 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 expression 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 pattern
			     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 or if it 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 problem.

       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 system 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 nonsignificant zeros sup-
	       pressed.  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 posi-
	      tional specifier and is intended primarily for use in translated versions of format
	      strings, not in the original 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 spa-
	      ces.  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
	      significant  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 precision, supply the count$ after the * in  the  format  string.   For  example,
       "%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 generator.

   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	sequential  inte-
			       gers starting with 1. If the optional destination array d is spec-
			       ified, 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 values  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 beginning 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  supplied,	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 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 expression r in the string
			       t,  substitute  the  string  s, and return the number of substitu-
			       tions.  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 discussion of the rules for
			       &'s and backslashes in the replacement text of sub(), gsub(),  and
			       gensub().)

       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  cor-
			       responding  parenthesized subexpression in r.  The 0'th element of
			       a contains the portion 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
			       matching substring.

       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 identically 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 functions 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 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 stan-
		 dard 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 available 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 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.

   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'' locations (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 cate-
	      gory.  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 sup-
	      ply 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 sup-
	      ply 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 for-
       mal  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  provision  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 follow the function
       name, without any intervening whitespace.  This avoids a syntactic ambiguity with the con-
       catenation  operator.   This  restriction  does not apply to the built-in functions listed
       above.

       Functions may call each other and may be recursive.  Function  parameters  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.

       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 variable.  Then use the variable as if it
       were the name of a function, prefixed 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 functions 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 --pro-
       file option.  It then continues to run.	SIGHUP causes pgawk to dump the profile and func-
       tion 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 underscores.

       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 corresponding .mo files.

       The internationalization features are described in full detail in GAWK: Effective AWK Pro-
       gramming.

POSIX COMPATIBILITY
       A primary goal for gawk is compatibility with the POSIX standard, as well as with the lat-
       est version of UNIX awk.  To this end, gawk incorporates the following user  visible  fea-
       tures  which are not described in the AWK book, but are part of the Bell Laboratories ver-
       sion 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 ear-
       lier implementations, when such an assignment appeared before any file names, the  assign-
       ment  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 argu-
       ments.  In compatibility mode, it warns about but otherwise 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.   There-
       fore 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  Labo-
       ratories version); the tolower() and toupper() built-in functions (from the Bell Laborato-
       ries 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 supports: It is possible
       to call the length() built-in function not only with no argument, but even without  paren-
       theses!	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.

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

       o There is no facility for doing file inclusion (gawk's @include mechanism).

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

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

       o Octal and hexadecimal constants in AWK programs.

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

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

       o The FIELDWIDTHS variable and fixed-width field splitting.

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

       o The PROCINFO array is not available.

       o The use of RS as a regular expression.

       o The special file names available for I/O redirection are not recognized.

       o The |& operator for creating co-processes.

       o The BEGINFILE and ENDFILE special patterns are not available.

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

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

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

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

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

       o The ability to pass an array to length().

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

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

       o The and(), asort(), asorti(), bindtextdomain(), compl(), dcgettext(), dcngettext(), gen-
	 sub(), lshift(), mktime(), or(), patsplit(), rshift(), strftime(), strtonum(), systime()
	 and xor() functions.

       o Localizable strings.

       o Adding new built-in functions dynamically with the extension() function.

       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 redirect-
       ion.

       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  separa-
       tor, 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 Wein-
       berger, 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 contrib-
       uted  a	number of bug fixes.  David Trueman, with contributions from Arnold Robbins, made
       gawk compatible with the new version of UNIX awk.  Arnold Robbins  is  the  current  main-
       tainer.

       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 sup-
       port 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.  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  setting  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 maintainer.

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

       Syntactically invalid single character programs tend to overflow the parse stack, generat-
       ing  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 during testing and
       debugging.  We thank him.

COPYING PERMISSIONS
       Copyright (C) 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 manual page into another
       language,  under  the  above conditions for modified versions, except that this permission
       notice may be stated in a translation approved by the Foundation.

Free Software Foundation		   Dec 07 2012					  GAWK(1)
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