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

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


       Gawk  is  the GNU Project's implementation of the AWK pro­
       gramming language.  It conforms to the definition  of  the
       language  in  the POSIX 1003.2 Command Language And Utili­
       ties 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  exten­
       sions, 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.


       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.  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.


       Gawk accepts the following options, listed alphabetically.

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

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

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

       -W copyleft
       -W copyright
              Print the short version of the GNU copyright infor­
              mation message on the standard output and exit suc­

       -W dump-variables[=file]
              Print  a  sorted  list  of  global variables, their
              types and final values to file.  If no file is pro­
              vided,  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 pro­
              grams.  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  inadver­
              tently  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

       -W help
       -W usage
              ally invalid are issued. (This is not fully  imple­
              mented yet.)

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

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

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

       -W posix
              This  turns on compatibility mode, with the follow­
              ing 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

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

              · The fflush() function is not available.

       -W profile[=prof_file]
              Send  profiling  data to prof_file.  The default is
              awkprof.out.  When run with gawk,  the  profile  is
              just  a  "pretty  printed"  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.

       -W re-interval
              option allows the easy intermixing of library func­
              tions  (used  via  the  -f and --file options) with
              source code entered on the  command  line.   It  is
              intended primarily for medium to large AWK programs
              used in shell scripts.

       -W version
              Print version information for this particular  copy
              of  gawk  on  the  standard output.  This is useful
              mainly for knowing if the current copy of  gawk  on
              your  system is up to date with respect to whatever
              the Free Software Foundation is distributing.  This
              is  also  useful when reporting bugs.  (Per the GNU
              Coding 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 is mainly for consistency
              with the argument parsing convention used  by  most
              other POSIX programs.
       In  compatibility  mode,  any other options are flagged as
       invalid, but are otherwise ignored.  In normal  operation,
       as long as program text has been supplied, unknown options
       are passed on to the AWK program in  the  ARGV  array  for
       processing.   This  is particularly useful for running AWK
       programs via the "#!" executable interpreter mechanism.


       An AWK program consists of a  sequence  of  pattern-action
       statements and optional function definitions.
              pattern   { action statements }
              function name(parameter list) { statements }
       Gawk  first  reads  the  program  source from the program-
       file(s) if 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  con­
       catenated 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  pro­
       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,
       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 pattern in the AWK program.  For each pattern
       that the record matches, the  associated  action  is  exe­
       cuted.  The patterns are tested in the order they occur in
       the program.
       Finally, after all the input is exhausted,  gawk  executes
       the code in the END block(s) (if any).


       AWK  variables  are dynamic; they come into existence when
       they are first used.  Their values  are  either  floating-
       point numbers or strings, or both, depending upon how they
       are used.  AWK also has  one  dimensional  arrays;  arrays
       with  multiple  dimensions may be simulated.  Several pre-
       defined variables are set as a program runs; these will be
       described as needed and summarized below.
       Normally,  records  are  separated  by newline characters.
       You can control how records  are  separated  by  assigning
       values  to  the built-in variable RS.  If RS is any single
       character, that character separates  records.   Otherwise,
       RS  is  a  regular  expression.   Text  in  the input that
       matches this  regular  expression  separates  the  record.
       However,  in  compatibility 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  new­
       line  character always acts as a field separator, in addi­
       tion to whatever value FS may have.
       As each input record is read, gawk splits the record  into
       fields,  using  the  value of the FS variable as the field
       separator.  If FS is a single character, fields are  sepa­
       rated  by  that character.  If FS is the null string, then
       each individual character becomes a separate field.   Oth­
       erwise,  FS  is  expected to be a full regular expression.
       In the special case that FS is a single space, fields  are
       separated  by  runs of spaces and/or tabs and/or newlines.
       (But see the discussion of  --posix,  below).   NOTE:  The
       value  of  IGNORECASE  (see below) also affects how fields
       are split when FS is a regular expression, and how records
       are separated when RS is a regular expression.
       If  the  FIELDWIDTHS  variable is set to a space separated
       list of 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 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.
       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
       ARGIND      The  index  in  ARGV of the current file being
       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  val­
                   ues  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 message.
       CONVFMT     The  conversion format for numbers, "%.6g", by
       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 pro­
                   grams which gawk spawns via redirection or the
                   system() function.
       ERRNO       If  a system error occurs either doing a redi­
                   rection for getline, during a  read  for  get­
                   line,  or  during  a  close(), then ERRNO will
                   contain a string describing  the  error.   The
                   value is subject to translation in non-English
       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 separator.
       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
                   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 ini­
                   tial value of IGNORECASE is zero, so all regu­
                   lar expression and string operations are  nor­
                   mally  case-sensitive.   Under  Unix, the full
                   ISO 8859-1 Latin-1 character set is used  when
                   ignoring case.
       LINT        Provides  dynamic control of the --lint option
                   from within an AWK program.  When  true,  gawk
                   prints lint warnings. When false, it does not.
                   When assigned the string value  "fatal",  lint
                   warnings  become  fatal  errors,  exactly like
                   --lint=fatal.   Any  other  true  value   just
                   prints warnings.
       NF          The  number  of  fields  in  the current input
       NR          The total number of input records seen so far.
       OFMT        The  output  format  for  numbers,  "%.6g", by
       OFS         The  output  field  separator,  a   space   by
       ORS         The output record separator, by default a new­
       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  ele­
                   ments 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
                                      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 cur­
                                      rent process.
                   PROCINFO["ppid"]   the parent  process  ID  of
                                      the current process.

       TEXTDOMAIN  The text domain of the AWK  program;  used  to
                   find  the  localized translations for the pro­
                   gram's strings.
       Arrays are subscripted with an expression  between  square
       brackets  ([  and  ]).  If the expression is an expression
       list (expr, expr ...)   then  the  array  subscript  is  a
       string  consisting  of  the  concatenation of the (string)
       value of each expression, separated by the  value  of  the
       SUBSEP variable.  This facility is used to simulate multi­
       ply 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 val­
       The  special  operator  in  may  be used in an if or while
       statement to see if an array has an index consisting of  a
       particular value.
              if (val in array)
                   print array[val]
       If the array has multiple subscripts, use (i, j) in array.
       The in construct may also be used in a for loop to iterate
       over all the elements of an array.
       An  element  may be deleted from an array using the delete
       statement.  The delete  statement  may  also  be  used  to
       delete the entire contents of an array, just by specifying
       the array name without a subscript.
   Variable Typing And Conversion
       Variables and fields may be (floating point)  numbers,  or
       strings,  or  both.  How the value of a variable is inter­
       preted 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  conver­
       sion  is  accomplished  using strtod(3).  A number is con­
       verted to a string by using the value of CONVFMT as a for­
       mat  string  for sprintf(3), with the numeric value of the
       variable as the argument.  However, even though  all  num­
       bers 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".
       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
       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 hexadecimal constants in your AWK program source
       code.  For example, the octal value 011 is equal to  deci­
       mal  9, and the hexadecimal value 0x11 is equal to decimal
   String Constants
       String  constants  in  AWK  are  sequences  of  characters
       enclosed  between double quotes (").  Within strings, cer­
       tain escape sequences are recognized, as in C.  These are:
       \\   A literal backslash.
       \a   The  "alert" character; usually the ASCII BEL charac­
       \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  hexadeci­
            mal  digits following the \x.  As in ANSI C, all fol­
            lowing hexadecimal digits are considered part of  the
            escape  sequence.  (This feature should tell us some­
            thing 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 reg­
       ular expressions (e.g., /[ \t\f\n\r\v]/ matches whitespace
       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/.


       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,
              relational expression
              pattern && pattern
              pattern || pattern
              pattern ? pattern : pattern
              ! pattern
              pattern1, pattern2
       BEGIN and END are two special kinds of patterns which  are
       not  tested  against  the  input.  The action parts of all
       BEGIN patterns are merged as if  all  the  statements  had
       been  written  in a single BEGIN block.  They are executed
       before any of the input is read.  Similarly, all  the  END
       blocks  are  merged,  and  executed  when all the input is
       exhausted (or when an exit statement is executed).   BEGIN
       and END patterns cannot be combined with other patterns in
       pattern expressions.  BEGIN and END patterns  cannot  have
       missing action parts.
       For  /regular  expression/ patterns, the associated state­
       ment 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  expres­
       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 combin­
       ing more primitive pattern expressions.  As in  most  lan­
       guages,  parentheses  may  be  used to change the order of
       The ?: operator is like the same operator in  C.   If  the
       first pattern is true then the pattern used for testing is
       the second pattern, 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 com­
       bine 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...]  negated  character  list, matches any character
                  except abc....
                  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  begin­
                  ning or the end of a word.

       \B         matches the empty string within a word.

       \<         matches  the empty string at the beginning of a

       \>         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-con­

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

       \'         matches the  empty  string  at  the  end  of  a

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

       Character classes are a  new  feature  introduced  in  the
       POSIX  standard.   A character class is a special notation
       for describing lists of characters 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 keyword denoting the  class,  and
       :].   The  character classes defined by the POSIX standard

       [:alnum:]  Alphanumeric characters.

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

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

       [:upper:]  Upper-case alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

       For example, before the POSIX standard, to match  alphanu­
       meric   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.

       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 sev­
       eral characters that  are  equivalent  for  collating,  or
       sorting,  purposes.   (E.g.,  in French, a plain "e" and a
       grave-accented e` are equivalent.)

       Collating Symbols
              A collating symbol is a  multi-character  collating
              element enclosed in [.  and .].  For example, if ch
              is a collating 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 charac­
       ter  classes;  they  do not recognize collating symbols or
       equivalence classes.

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

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

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

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

       The  operators  in AWK, in order of decreasing precedence,

       (...)       Grouping

       $           Field reference.

       ++ --       Increment and decrement, both prefix and post­

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

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

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

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

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

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

   Control Statements
       The control statements are as follows:

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

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

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

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

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

       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

                             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 out­
                             put 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 ter­
                             minated with the value  of  the  ORS

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

       printf fmt, expr-list Format and print.

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

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

       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

       Additional output redirections are allowed for  print  and

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

       print ... | command
              writes on a pipe.

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

       The  getline command returns 0 on end of file and -1 on an
       error.  Upon an error, ERRNO contains a string  describing
               is numeric, it  is  treated  as  a  character  and
               printed.  Otherwise, the argument is assumed to be
               a string, and the only  first  character  of  that
               string is printed.

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

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

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

       %g ,  %G
               Use %e or %f  conversion,  whichever  is  shorter,
               with nonsignificant zeros suppressed.  The %G for­
               mat uses %E instead of %e.

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

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

       %s      A character string.

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

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

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

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

       count$ Use the count'th argument at this point in the for­
              matting.  This is called a positional specifier and
              is  intended  primarily  for use in translated ver­
              sions 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

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

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

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

       .prec  A  number  that specifies the precision to use when
              printing.  For the %e, %E,  and  %f  formats,  this
              specifies  the number of digits you want printed to
              the right of the decimal point.  For the %g, and %G
              formats, it specifies the maximum number of signif­
              icant 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

       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  preci­
       sion,  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

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

       /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  informa­
       tion 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 current process, in decimal,  termi­
                   nated with a newline.

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

       /dev/user   Reading this file returns a single record ter­
                   minated with a newline.  The fields are  sepa­
                   rated  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

       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  radi­
       asort(s [, d])          Returns  the number of elements in
                               the source array s.  The  contents
                               of  s are sorted using gawk's nor­
                               mal rules  for  comparing  values,
                               and the indexes of the sorted val­
                               ues of s are replaced with sequen­
                               tial  integers starting with 1. If
                               the optional destination  array  d
                               is  specified,  then  s  is  first
                               duplicated into d, and then  d  is
                               sorted, leaving the indexes of the
                               source array s unchanged.

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

       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 sup­
                               plied, $0 is used instead.  Within
                               the   replacement   text   s,  the
                               sequence \n, where n  is  a  digit
                               from  1 to 9, may be used to indi­
                               cate just the  text  that  matched
                               the  n'th parenthesized subexpres­
                               sion.  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
                               acter indices start at one.)

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

       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 provided,
                               a is cleared and then  elements  1
                               through n are filled with the por­
                               tions of s that match  the  corre­
                               sponding  parenthesized subexpres­
                               sion in r.  The 0'th element of  a
                               contains  the portion of s matched
                               by the entire  regular  expression
                               r.   Subscripts a[n, "start"], and
                               a[n, "length"] provide the  start­
                               ing index in the string and length
                               respectively,  of  each   matching

       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

       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

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

                 Turns datespec into a time  stamp  of  the  same
                 form  as returned by systime().  The datespec is
                 a string of the form YYYY MM DD HH MM SS[  DST].
                 The contents of the string are six or seven num­
                 bers representing  respectively  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, and
                 the second from 0 to 60, and  an  optional  day­
                 light  saving flag.  The values of these numbers
                 need not be within  the  ranges  specified;  for
                 example,  an hour of -1 means 1 hour before mid­
                 night.  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 day­
                 light  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 speci­
                 fied  time.  If datespec does not contain enough
                 elements or if the  resulting  time  is  out  of
                 range, mktime() returns -1.

       strftime([format [, timestamp]])
                 Formats timestamp according to the specification
                 in format.  The timestamp should be of the  same
                 form  as returned by systime().  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 spec­
                 ification  for the strftime() function in ANSI C
                 for the format conversions that  are  guaranteed
                 to  be  available.   A  public-domain version of
                 strftime(3) and a man  page  for  it  come  with
                 gawk;  if  that  version was used to build gawk,
                 then all of the conversions  described  in  that
                 man page are available to gawk.

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

       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: Effec­
       tive 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'' locations (e.g.,  during
              testing).  It returns the directory where domain is
              The default domain is the value of TEXTDOMAIN.   If
              directory is the null string (""), then bindtextdo­
              main() returns the current binding  for  the  given

       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 TEXTDO­
              MAIN.  The default value for category  is  "LC_MES­
              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 [, cate­
              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  TEXTDO­
              MAIN.   The  default value for category is "LC_MES­
              If you supply a value for category, it  must  be  a
              string  equal to one of the known locale categories


       Since  functions  were not originally part of the AWK lan­
       guage, 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 inter­
       vening white space.  This is to avoid a syntactic  ambigu­
       ity  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.  Func­
       tion parameters used as local variables are initialized to
       the null string and the number zero upon function  invoca­

       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 functions at parse time, instead of at run time.
       Calling  an  undefined  function  at  run  time is a fatal

       The word func may be used in place of function.


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

       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 pro­
               vided  as  strings.  Returns the value returned by


       Print and sort the login names of all users:

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

       Count lines in a file:

                 { nlines++ }
            END  { print nlines }

       Precede each line by its number in the file:

            { print FNR, $0 }

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

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

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


       String  constants  are sequences of characters enclosed in
       double quotes.  In non-English speaking  environments,  it
       is  possible to mark strings in the AWK program as requir­
       ing translation  to  the  native  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  mes­
           sages  text  domain,  which  likely  does  not contain

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


       A  primary  goal  for gawk is compatibility with the POSIX
       standard, as well as with the latest version of UNIX  awk.
       To  this end, gawk incorporates 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.   How­
       ever,  in earlier implementations, when such an assignment
       appeared before any file names, the assignment would  hap­
       pen  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 applica­
       tions  that depended upon the old behavior.  (This feature
       was agreed upon by both the Bell Laboratories and the  GNU

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

       When processing arguments, gawk uses  the  special  option
       "--"  to  signal  the  end of arguments.  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.  Therefore
       srand() in gawk also returns its current seed.

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


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

       usage  as equivalent to the next statement.  Gawk supports
       this usage if --traditional has been specified.


       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  --tradi­
       tional option.

       The  following features of gawk are not available in POSIX

       · 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.

         variables are not special.

       · The IGNORECASE variable and  its  side-effects  are  not

       · The  FIELDWIDTHS  variable  and fixed-width field split­

       · 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 recognized.

       · 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  argu­
         ment 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

       · 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 redi­

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


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

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


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

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

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


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

       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
       the current 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  Darrel
       Hankerson.   Fred  Fish  supplied  support  for the Amiga,
       Stephen Davies provided the Tandem port, and Martin  Brown
       provided the BeOS port.


       This man page documents gawk, version 3.1.3.


       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 --ver­
       sion), what C compiler you used to compile it, and a  test
       program  and data that are as small as possible for repro­
       ducing the problem.

       Before sending a bug report, please do two things.  First,
       verify  that  you  have  the latest version of gawk.  Many
       bugs (usually subtle ones) are fixed at each release,  and
       if yours is out of date, the problem may already have been
       solved.  Second, please read this man page and the  refer­
       ence  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 unre­
       liable  way to report bugs.  Instead, please use the elec­
       tronic mail addresses given above.


       Brian Kernighan of  Bell  Laboratories  provided  valuable
       assistance during testing and debugging.  We thank him.


       Copyright  ©  1989,  1991,  1992,  1993, 1994, 1995, 1996,
       1997, 1998, 1999, 2001, 2002, 2003 Free  Software  Founda­
       tion, 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 ver­
       sions of this manual page under the conditions for  verba­
       tim  copying,  provided  that the entire resulting derived
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