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    Command:

    gawk

    
    
    

    SYNOPSIS

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

    DESCRIPTION

           Gawk  is  the  GNU Project's implementation of the AWK programming lan-
           guage.  It conforms to the definition of  the  language  in  the  POSIX
           1003.1  Standard.   This version in turn is based on the description in
           The AWK Programming Language, by Aho, Kernighan, and  Weinberger,  with
           the additional features found in the System V Release 4 version of UNIX
           awk.  Gawk also provides more recent Bell Laboratories awk  extensions,
           and a number of GNU-specific extensions.
    
           Pgawk  is  the profiling version of gawk.  It is identical in every way
           to gawk, except that programs run more  slowly,  and  it  automatically
           produces  an  execution profile in the file awkprof.out when done.  See
           the --profile option, below.
    
           The command line consists of options to gawk itself,  the  AWK  program
           text  (if  not supplied via the -f or --file options), and values to be
           made available in the ARGC and ARGV pre-defined AWK variables.
    
    
    

    OPTION FORMAT

           Gawk options may be either traditional POSIX  one  letter  options,  or
           GNU-style  long  options.  POSIX options start with a single "-", while
           long options start with "--".  Long options are provided for both  GNU-
           specific features and for POSIX-mandated features.
    
           Following  the  POSIX  standard, gawk-specific options are supplied via
           arguments to the -W option.  Multiple -W options may be  supplied  Each
           -W  option  has  a corresponding long option, as detailed below.  Argu-
           ments to long options are either joined with the option by an  =  sign,
           with no intervening spaces, or they may be provided in the next command
           line argument.  Long options may be abbreviated, as long as the  abbre-
           viation remains unique.
    
    
    

    OPTIONS

           Gawk accepts the following options, listed by frequency.
    
           -F fs
           --field-separator fs
                  Use fs for the input field separator (the value of the FS prede-
                  fined variable).
    
           -v var=val
           --assign var=val
                  Assign the value val to the variable var,  before  execution  of
                  the  program  begins.  Such variable values are available to the
                  BEGIN block of an AWK program.
                  (Current  versions of the Bell Laboratories awk no longer accept
                  them.)
    
           -O
           --optimize
                  Enable optimizations upon the  internal  representation  of  the
                  program.  Currently, this includes just simple constant-folding.
                  The gawk maintainer hopes to add additional  optimizations  over
                  time.
    
           -W compat
           -W traditional
           --compat
           --traditional
                  Run  in compatibility mode.  In compatibility mode, gawk behaves
                  identically to UNIX awk; none of the GNU-specific extensions are
                  recognized.   The  use  of  --traditional  is preferred over the
                  other forms of this option.  See GNU EXTENSIONS, below, for more
                  information.
    
           -W copyleft
           -W copyright
           --copyleft
           --copyright
                  Print the short version of the GNU copyright information message
                  on the standard output and exit successfully.
    
           -W dump-variables[=file]
           --dump-variables[=file]
                  Print a sorted list of global variables, their types  and  final
                  values  to file.  If no file is provided, gawk uses a file named
                  awkvars.out in the current directory.
                  Having a list of all the global variables is a good way to  look
                  for  typographical  errors in your programs.  You would also use
                  this option if you have a large program with a lot of functions,
                  and  you want to be sure that your functions don't inadvertently
                  use global variables that you meant to be  local.   (This  is  a
                  particularly  easy  mistake  to  make with simple variable names
                  like i, j, and so on.)
    
           -W exec file
           --exec file
                  Similar to -f, however, this is option  is  the  last  one  pro-
                  cessed.   This should be used with #!  scripts, particularly for
                  CGI applications, to avoid passing in options or source code (!)
                  on  the  command line from a URL.  This option disables command-
                  line variable assignments.
    
           -W gen-po
           --gen-po
                  Scan and parse the AWK program, and generate a  GNU  .po  format
                  file on standard output with entries for all localizable strings
                  portable to other AWK implementations.  With an  optional  argu-
                  ment  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.)
    
           -W lint-old
           --lint-old
                  Provide  warnings  about constructs that are not portable to the
                  original version of Unix awk.
    
           -W non-decimal-data
           --non-decimal-data
                  Recognize octal and hexadecimal values in input data.  Use  this
                  option with great caution!
    
           -W posix
           --posix
                  This  turns on compatibility mode, with the following additional
                  restrictions:
    
                  ? \x escape sequences are not recognized.
    
                  ? Only space and tab act as field separators when FS is set to a
                    single space, newline does not.
    
                  ? You cannot continue lines after ?  and :.
    
                  ? The synonym func for the keyword function is not recognized.
    
                  ? The  operators ** and **= cannot be used in place of ^ and ^=.
    
                  ? The fflush() function is not available.
    
           -W profile[=prof_file]
           --profile[=prof_file]
                  Send profiling data to prof_file.  The default  is  awkprof.out.
                  When  run with gawk, the profile is just a "pretty printed" ver-
                  sion of the program.  When run with pgawk, the profile  contains
                  execution  counts  of  each statement in the program in the left
                  margin and function call counts for each user-defined  function.
    
           -W re-interval
           --re-interval
                  Enable  the  use  of  interval expressions in regular expression
                  matching (see Regular Expressions, below).  Interval expressions
                  were not traditionally available in the AWK language.  The POSIX
                  standard added them, to make awk and egrep consistent with  each
                  other.   However, their use is likely to break old AWK programs,
                  so gawk only provides them  if  they  are  requested  with  this
                  option, or when --posix is specified.
                  default is to follow traditional behavior and use  a  period  as
                  the  decimal  point, even in locales where the period is not the
                  decimal point character.   This  option  overrides  the  default
                  behavior,  without  the full draconian strictness of the --posix
                  option.
    
           -W version
           --version
                  Print version information for this particular copy  of  gawk  on
                  the  standard  output.  This is useful mainly for knowing if the
                  current copy of gawk on your system is up to date  with  respect
                  to  whatever the Free Software Foundation is distributing.  This
                  is also useful when reporting bugs.  (Per the GNU  Coding  Stan-
                  dards, these options cause an immediate, successful exit.)
    
           --     Signal the end of options. This is useful to allow further argu-
                  ments to the AWK program itself to start with a "-".  This  pro-
                  vides  consistency  with the argument parsing convention used by
                  most other POSIX programs.
    
           In compatibility mode, any other options are flagged  as  invalid,  but
           are  otherwise  ignored.   In normal operation, as long as program text
           has been supplied, unknown options are passed on to the AWK program  in
           the ARGV array for processing.  This is particularly useful for running
           AWK programs via the "#!" executable interpreter mechanism.
    
    
    

    AWK PROGRAM EXECUTION

           An AWK program consists of a sequence of pattern-action statements  and
           optional function definitions.
    
                  pattern   { action statements }
                  function name(parameter list) { statements }
    
           Gawk  first reads the program source from the program-file(s) if speci-
           fied, from arguments to --source, or from the first non-option argument
           on  the command line.  The -f and --source options may be used multiple
           times on the command line.  Gawk reads the program text as if  all  the
           program-files  and  command  line  source  texts  had been concatenated
           together.  This is useful for  building  libraries  of  AWK  functions,
           without  having to include them in each new AWK program that uses them.
           It also provides the ability to mix library functions with command line
           programs.
    
           The  environment  variable  AWKPATH specifies a search path to use when
           finding source files named with the -f option.  If this  variable  does
           not  exist,  the default path is ".:/usr/local/share/awk".  (The actual
           directory may vary, depending upon how gawk was built  and  installed.)
           If a file name given to the -f option contains a "/" character, no path
           search is performed.
    
           Gawk executes AWK programs in the following order.  First, all variable
           assignments specified via the -v option are performed.  Next, gawk com-
           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 executed.  The  patterns  are  tested  in  the
           order they occur in the program.
    
           Finally,  after  all  the input is exhausted, gawk executes the code in
           the END block(s) (if any).
    
    
    

    VARIABLES, RECORDS AND FIELDS

           AWK variables are dynamic; they come into existence when they are first
           used.   Their  values  are either floating-point numbers or strings, or
           both, depending upon how they are used.  AWK also has  one  dimensional
           arrays; arrays with multiple dimensions may be simulated.  Several pre-
           defined variables are set as a program runs;  these  are  described  as
           needed and summarized below.
    
       Records
           Normally, records are separated by newline characters.  You can control
           how records are separated by assigning values to the built-in  variable
           RS.   If  RS is any single character, that character separates records.
           Otherwise, RS is a regular expression.  Text in the input that  matches
           this  regular expression separates the record.  However, in compatibil-
           ity mode, only the first character of its string value is used for sep-
           arating  records.   If  RS  is set to the null string, then records are
           separated by blank lines.  When RS is set to the null string, the  new-
           line  character  always acts as a field separator, in addition to what-
           ever value FS may have.
    
       Fields
           As each input record is read, gawk splits the record into fields, using
           the value of the FS variable as the field separator.  If FS is a single
           character, fields are separated by that character.  If FS is  the  null
           string,  then each individual character becomes a separate field.  Oth-
           erwise, FS is expected to be a full regular expression.  In the special
           case  that FS is a single space, fields are separated by runs of spaces
           and/or tabs and/or newlines.  (But see the section POSIX COMPATIBILITY,
           below).   NOTE:  The  value  of IGNORECASE (see below) also affects how
           fields are split when FS is a regular expression, and how  records  are
           separated when RS is a regular expression.
    
           If  the  FIELDWIDTHS  variable is set to a space separated list of num-
           bers, each field is expected to have fixed width, and  gawk  splits  up
           the  record  using  the  specified widths.  The value of FS is ignored.
           Assigning a new value to FS  overrides  the  use  of  FIELDWIDTHS,  and
           restores the default behavior.
    
           Each  field  in the input record may be referenced by its position, $1,
           $2, and so on.  $0 is the whole record.  Fields need not be  referenced
           by constants:
    
           causes the values of fields past the new value  to  be  lost,  and  the
           value  of  $0  to be recomputed, with the fields being separated by the
           value of OFS.
    
           Assigning a value to an existing field causes the whole  record  to  be
           rebuilt  when  $0  is  referenced.   Similarly, assigning a value to $0
           causes the record to be resplit, creating new values for the fields.
    
       Built-in Variables
           Gawk's built-in variables are:
    
           ARGC        The number of command  line  arguments  (does  not  include
                       options to gawk, or the program source).
    
           ARGIND      The index in ARGV of the current file being processed.
    
           ARGV        Array of command line arguments.  The array is indexed from
                       0 to ARGC - 1.  Dynamically changing the contents  of  ARGV
                       can control the files used for data.
    
           BINMODE     On  non-POSIX  systems,  specifies use of "binary" mode for
                       all file I/O.  Numeric values of 1, 2, or 3,  specify  that
                       input  files,  output  files,  or  all files, respectively,
                       should use binary I/O.  String values of "r", or "w"  spec-
                       ify that input files, or output files, respectively, should
                       use binary I/O.  String values of "rw" or "wr" specify that
                       all files should use binary I/O.  Any other string value is
                       treated as "rw", but generates a warning message.
    
           CONVFMT     The conversion format for numbers, "%.6g", by default.
    
           ENVIRON     An array containing the values of the current  environment.
                       The  array  is  indexed  by the environment variables, each
                       element being the  value  of  that  variable  (e.g.,  ENVI-
                       RON["HOME"]  might  be  /home/arnold).  Changing this array
                       does not affect the environment seen by programs which gawk
                       spawns via redirection or the system() function.
    
           ERRNO       If  a  system  error  occurs either doing a redirection for
                       getline, during a read for getline, or  during  a  close(),
                       then ERRNO will contain a string describing the error.  The
                       value is subject to translation in non-English locales.
    
           FIELDWIDTHS A white-space separated list  of  fieldwidths.   When  set,
                       gawk  parses  the input into fields of fixed width, instead
                       of using the value of the FS variable as the field  separa-
                       tor.
    
           FILENAME    The name of the current input file.  If no files are speci-
                       fied on the command line, the value  of  FILENAME  is  "-".
                       However,  FILENAME  is  undefined  inside  the  BEGIN block
                       tions.  NOTE: Array subscripting is not affected.  However,
                       the asort() and asorti() functions are affected.
                       Thus,  if IGNORECASE is not equal to zero, /aB/ matches all
                       of the strings "ab", "aB", "Ab", and "AB".  As with all AWK
                       variables,  the initial value of IGNORECASE is zero, so all
                       regular expression and string operations are normally case-
                       sensitive.  Under Unix, the full ISO 8859-1 Latin-1 charac-
                       ter set is used when ignoring case.  As of gawk 3.1.4,  the
                       case  equivalencies  are fully locale-aware, based on the C
                       <ctype.h> facilities such as isalpha(), and toupper().
    
           LINT        Provides dynamic control of the --lint option  from  within
                       an AWK program.  When true, gawk prints lint warnings. When
                       false,  it  does  not.   When  assigned  the  string  value
                       "fatal",  lint  warnings  become fatal errors, exactly like
                       --lint=fatal.  Any other true value just prints warnings.
    
           NF          The number of fields in the current input record.
    
           NR          The total number of input records seen so far.
    
           OFMT        The output format for numbers, "%.6g", by default.
    
           OFS         The output field separator, a space by default.
    
           ORS         The output record separator, by default a newline.
    
           PROCINFO    The elements of this array provide  access  to  information
                       about  the running AWK program.  On some systems, there may
                       be elements in the array,  "group1"  through  "groupn"  for
                       some  n,  which  is the number of supplementary groups that
                       the process has.  Use the in operator  to  test  for  these
                       elements.   The  following  elements  are  guaranteed to be
                       available:
    
                       PROCINFO["egid"]   the value of the getegid(2) system call.
    
                       PROCINFO["euid"]   the value of the geteuid(2) system call.
    
                       PROCINFO["FS"]     "FS" if field splitting with  FS  is  in
                                          effect, or "FIELDWIDTHS" if field split-
                                          ting with FIELDWIDTHS is in effect.
    
                       PROCINFO["gid"]    the value of the getgid(2) system  call.
    
                       PROCINFO["pgrpid"] the process group ID of the current pro-
                                          cess.
    
                       PROCINFO["pid"]    the process ID of the current process.
    
                       PROCINFO["ppid"]   the parent process  ID  of  the  current
                                          process.
    
                       no match.  (This implies that character  indices  start  at
                       one.)
    
           RLENGTH     The  length  of  the  string  matched  by match(); -1 if no
                       match.
    
           SUBSEP      The character used to separate multiple subscripts in array
                       elements, by default "\034".
    
           TEXTDOMAIN  The text domain of the AWK program; used to find the local-
                       ized translations for the program's strings.
    
       Arrays
           Arrays are subscripted with an expression between  square  brackets  ([
           and ]).  If the expression is an expression list (expr, expr ...)  then
           the array subscript is a string consisting of the concatenation of  the
           (string) value of each expression, separated by the value of the SUBSEP
           variable.  This facility  is  used  to  simulate  multiply  dimensioned
           arrays.  For example:
    
                  i = "A"; j = "B"; k = "C"
                  x[i, j, k] = "hello, world\n"
    
           assigns the string "hello, world\n" to the element of the array x which
           is indexed by the string "A\034B\034C".  All arrays in AWK are associa-
           tive, i.e. indexed by string values.
    
           The  special  operator  in may be used to test if an array has an index
           consisting of a particular value.
    
                  if (val in array)
                       print array[val]
    
           If the array has multiple subscripts, use (i, j) in array.
    
           The in construct may also be used in a for loop to iterate over all the
           elements of an array.
    
           An  element  may  be  deleted from an array using the delete statement.
           The delete statement may also be used to delete the entire contents  of
           an array, just by specifying the array name without a subscript.
    
       Variable Typing And Conversion
           Variables  and  fields  may be (floating point) numbers, or strings, or
           both.  How the value of a variable is interpreted depends upon its con-
           text.  If used in a numeric expression, it will be treated as a number;
           if used as a string it will be treated as a string.
    
           To force a variable to be treated as a number, add 0 to it; to force it
           to be treated as a string, concatenate it with the null string.
    
           When  a  string must be converted to a number, the conversion is accom-
           numbers are treated: the decimal separator of the numbers you are feed-
           ing  to  gawk  must  conform  to what your locale would expect, be it a
           comma (,) or a period (.).
    
           Gawk performs comparisons as follows: If  two  variables  are  numeric,
           they  are  compared numerically.  If one value is numeric and the other
           has a string value that is a "numeric  string,"  then  comparisons  are
           also  done numerically.  Otherwise, the numeric value is converted to a
           string and a string comparison is performed.  Two strings are compared,
           of course, as strings.
    
           Note that string constants, such as "57", are not numeric strings, they
           are string constants.  The idea of "numeric  string"  only  applies  to
           fields,  getline  input,  FILENAME, ARGV elements, ENVIRON elements and
           the elements of an array created by split() that are  numeric  strings.
           The  basic  idea  is  that  user input, and only user input, that looks
           numeric, should be treated that way.
    
           Uninitialized variables have the numeric value 0 and the  string  value
           "" (the null, or empty, string).
    
       Octal and Hexadecimal Constants
           Starting  with version 3.1 of gawk , you may use C-style octal and hex-
           adecimal constants in your AWK program source code.  For  example,  the
           octal  value  011 is equal to decimal 9, and the hexadecimal value 0x11
           is equal to decimal 17.
    
       String Constants
           String constants in AWK are sequences of  characters  enclosed  between
           double quotes (").  Within strings, certain escape sequences are recog-
           nized, as in C.  These are:
    
           \\   A literal backslash.
    
           \a   The "alert" character; usually the ASCII BEL character.
    
           \b   backspace.
    
           \f   form-feed.
    
           \n   newline.
    
           \r   carriage return.
    
           \t   horizontal tab.
    
           \v   vertical tab.
    
           \xhex digits
                The character represented by the string of hexadecimal digits fol-
                lowing the \x.  As in ANSI C, all following hexadecimal digits are
    
           expression constants.  Thus, /a\52b/ is equivalent to /a\*b/.
    
    
    

    PATTERNS AND ACTIONS

           AWK is a line-oriented language.  The pattern comes first, and then the
           action.  Action statements are enclosed in { and }.  Either the pattern
           may be missing, or the action may be missing, but, of course, not both.
           If  the  pattern  is  missing,  the action is executed for every single
           record of input.  A missing action is equivalent to
    
                  { print }
    
           which prints the entire record.
    
           Comments begin with the "#" character, and continue until  the  end  of
           the line.  Blank lines may be used to separate statements.  Normally, a
           statement ends with a newline, however, this is not the case for  lines
           ending  in  a ",", {, ?, :, &&, or ||.  Lines ending in do or else also
           have their statements automatically continued on  the  following  line.
           In  other  cases,  a  line can be continued by ending it with a "\", in
           which case the newline will be ignored.
    
           Multiple statements may be put on one line by separating  them  with  a
           ";".   This  applies to both the statements within the action part of a
           pattern-action pair (the usual case), and to the pattern-action  state-
           ments themselves.
    
       Patterns
           AWK patterns may be one of the following:
    
                  BEGIN
                  END
                  /regular expression/
                  relational expression
                  pattern && pattern
                  pattern || pattern
                  pattern ? pattern : pattern
                  (pattern)
                  ! pattern
                  pattern1, pattern2
    
           BEGIN  and  END  are two special kinds of patterns which are not tested
           against the input.  The action parts of all BEGIN patterns  are  merged
           as  if  all  the  statements  had been written in a single BEGIN block.
           They are executed before any of the input is read.  Similarly, all  the
           END blocks are merged, and executed when all the input is exhausted (or
           when an exit statement is executed).  BEGIN and END patterns cannot  be
           combined  with  other  patterns  in pattern expressions.  BEGIN and END
           patterns cannot have missing action parts.
    
           For /regular expression/ patterns, the associated statement is executed
           for  each  input  record  that matches the regular expression.  Regular
           expressions are the same as  those  in  egrep(1),  and  are  summarized
           wise  it  is  the  third.  Only one of the second and third patterns is
           evaluated.
    
           The pattern1, pattern2 form of an expression is called a range pattern.
           It  matches  all input records starting with a record that matches pat-
           tern1, and continuing until a record that matches pattern2,  inclusive.
           It does not combine with any other sort of pattern expression.
    
       Regular Expressions
           Regular  expressions  are  the  extended kind found in egrep.  They are
           composed of characters as follows:
    
           c          matches the non-metacharacter c.
    
           \c         matches the literal character c.
    
           .          matches any character including newline.
    
           ^          matches the beginning of a string.
    
           $          matches the end of a string.
    
           [abc...]   character list, matches any of the characters abc....
    
           [^abc...]  negated character list, matches any character except abc....
    
           r1|r2      alternation: matches either r1 or r2.
    
           r1r2       concatenation: matches r1, and then r2.
    
           r+         matches one or more r's.
    
           r*         matches zero or more r's.
    
           r?         matches zero or one r's.
    
           (r)        grouping: matches r.
    
           r{n}
           r{n,}
           r{n,m}     One  or two numbers inside braces denote an interval expres-
                      sion.  If there is one number in the braces,  the  preceding
                      regular  expression r is repeated n times.  If there are two
                      numbers separated by a comma, r is repeated n  to  m  times.
                      If  there  is  one  number  followed  by  a comma, then r is
                      repeated at least n times.
                      Interval expressions are only available if either --posix or
                      --re-interval is specified on the command line.
    
           \y         matches  the empty string at either the beginning or the end
                      of a word.
    
           \'         matches the empty string at the end of a buffer.
    
           The escape sequences that are valid in string constants (see below) are
           also valid in regular expressions.
    
           Character  classes  are  a feature introduced in the POSIX standard.  A
           character class is a special notation for describing lists  of  charac-
           ters  that  have  a specific attribute, but where the actual characters
           themselves can vary from country to country and/or from  character  set
           to  character  set.   For  example, the notion of what is an alphabetic
           character differs in the USA and in France.
    
           A character class is only valid in  a  regular  expression  inside  the
           brackets  of a character list.  Character classes consist of [:, a key-
           word denoting the class, and :].  The character classes defined by  the
           POSIX standard are:
    
           [:alnum:]  Alphanumeric characters.
    
           [:alpha:]  Alphabetic characters.
    
           [:blank:]  Space or tab characters.
    
           [:cntrl:]  Control characters.
    
           [:digit:]  Numeric characters.
    
           [:graph:]  Characters that are both printable and visible.  (A space is
                      printable, but not visible, while an a is both.)
    
           [:lower:]  Lower-case alphabetic characters.
    
           [:print:]  Printable characters (characters that are not control  char-
                      acters.)
    
           [:punct:]  Punctuation characters (characters that are not letter, dig-
                      its, control characters, or space characters).
    
           [:space:]  Space characters (such as space, tab, and formfeed, to  name
                      a few).
    
           [:upper:]  Upper-case alphabetic characters.
    
           [:xdigit:] Characters that are hexadecimal digits.
    
           For  example,  before the POSIX standard, to match alphanumeric charac-
           ters, you would have had to write /[A-Za-z0-9]/.  If your character set
           had  other  alphabetic characters in it, this would not match them, and
           if your character set collated differently from ASCII, this  might  not
           even match the ASCII alphanumeric characters.  With the POSIX character
           classes, you can write /[[:alnum:]]/, and this matches  the  alphabetic
           and numeric characters in your character set, no matter what it is.
    
           Equivalence Classes
                  An equivalence class is a locale-specific name  for  a  list  of
                  characters  that are equivalent.  The name is enclosed in [= and
                  =].  For example, the name e might be used to represent  all  of
                  "e,"  "?,"  and "`."  In this case, [[=e=]] is a regular expres-
                  sion that matches any of e, ?, or `.
    
           These features are very valuable in non-English speaking locales.   The
           library  functions  that gawk uses for regular expression matching cur-
           rently only recognize POSIX character classes; they  do  not  recognize
           collating symbols or equivalence classes.
    
           The  \y, \B, \<, \>, \w, \W, \', and \' operators are specific to gawk;
           they are extensions based on facilities in the GNU  regular  expression
           libraries.
    
           The various command line options control how gawk interprets characters
           in regular expressions.
    
           No options
                  In the default case, gawk provide all the  facilities  of  POSIX
                  regular  expressions  and  the  GNU regular expression operators
                  described above.  However, interval  expressions  are  not  sup-
                  ported.
    
           --posix
                  Only  POSIX regular expressions are supported, the GNU operators
                  are not special.  (E.g., \w  matches  a  literal  w).   Interval
                  expressions are allowed. PLEASE NOTE that the regular expression
                  [A-Z] will also match the lowercase  characters  in  this  case!
                  Consult  the  info  pages of  gawk  utility for more information
                  about this behaviour.
    
           --traditional
                  Traditional Unix awk regular expressions are matched.   The  GNU
                  operators  are  not special, interval expressions are not avail-
                  able, and neither are the POSIX character  classes  ([[:alnum:]]
                  and  so  on).   Characters  described  by  octal and hexadecimal
                  escape sequences are treated literally, even if  they  represent
                  regular expression metacharacters.
    
           --re-interval
                  Allow  interval  expressions  in  regular  expressions,  even if
                  --traditional has been provided.
    
       Actions
           Action statements are enclosed in braces, { and }.   Action  statements
           consist  of  the  usual assignment, conditional, and looping statements
           found in  most  languages.   The  operators,  control  statements,  and
           input/output statements available are patterned after those in C.
    
    
           * / %       Multiplication, division, and modulus.
    
           + -         Addition and subtraction.
    
           space       String concatenation.
    
           | |&        Piped I/O for getline, print, and printf.
    
           < >
           <= >=
           != ==       The regular relational operators.
    
           ~ !~        Regular expression match, negated match.  NOTE: Do not  use
                       a constant regular expression (/foo/) on the left-hand side
                       of a ~ or !~.  Only use one on the  right-hand  side.   The
                       expression  /foo/  ~  exp  has  the  same meaning as (($0 ~
                       /foo/) ~ exp).  This is usually not what was intended.
    
           in          Array membership.
    
           &&          Logical AND.
    
           ||          Logical OR.
    
           ?:          The C conditional expression.  This has the  form  expr1  ?
                       expr2  : expr3.  If expr1 is true, the value of the expres-
                       sion is expr2, otherwise it is expr3.  Only  one  of  expr2
                       and expr3 is evaluated.
    
           = += -=
           *= /= %= ^= Assignment.   Both  absolute  assignment  (var = value) and
                       operator-assignment (the other forms) are supported.
    
       Control Statements
           The control statements are as follows:
    
                  if (condition) statement [ else statement ]
                  while (condition) statement
                  do statement while (condition)
                  for (expr1; expr2; expr3) statement
                  for (var in array) statement
                  break
                  continue
                  delete array[index]
                  delete array
                  exit [ expression ]
                  { statements }
    
       I/O Statements
           The input/output statements are as follows:
    
           command | getline [var]
                                 Run  command  piping the output either into $0 or
                                 var, as above.
    
           command |& getline [var]
                                 Run command as a  co-process  piping  the  output
                                 either  into  $0  or var, as above.  Co-processes
                                 are a gawk extension.  (command  can  also  be  a
                                 socket.   See  the subsection Special File Names,
                                 below.)
    
           next                  Stop processing the current  input  record.   The
                                 next  input  record is read and processing starts
                                 over with the first pattern in the  AWK  program.
                                 If  the end of the input data is reached, the END
                                 block(s), if any, are executed.
    
           nextfile              Stop processing the current input file.  The next
                                 input record read comes from the next input file.
                                 FILENAME and ARGIND are updated, FNR is reset  to
                                 1, and processing starts over with the first pat-
                                 tern in the AWK program. If the end of the  input
                                 data  is  reached,  the END block(s), if any, are
                                 executed.
    
           print                 Prints the current record.  The output record  is
                                 terminated with the value of the ORS variable.
    
           print expr-list       Prints expressions.  Each expression is separated
                                 by the value of the  OFS  variable.   The  output
                                 record  is  terminated  with the value of the ORS
                                 variable.
    
           print expr-list >file Prints expressions on file.  Each  expression  is
                                 separated  by the value of the OFS variable.  The
                                 output record is terminated with the value of the
                                 ORS variable.
    
           printf fmt, expr-list Format and print.
    
           printf fmt, expr-list >file
                                 Format and print on file.
    
           system(cmd-line)      Execute the command cmd-line, and return the exit
                                 status.  (This may not be available on  non-POSIX
                                 systems.)
    
           fflush([file])        Flush any buffers associated with the open output
                                 file or pipe file.   If  file  is  missing,  then
                                 standard  output is flushed.  If file is the null
                                 string, then all open output files and pipes have
                                 their buffers flushed.
    
           an  error.  Upon an error, ERRNO contains a string describing the prob-
           lem.
    
           NOTE: If using a pipe, co-process, or socket to getline, or from  print
           or  printf  within a loop, you must use close() to create new instances
           of the command or socket.  AWK  does  not  automatically  close  pipes,
           sockets, or co-processes when they return EOF.
    
       The printf Statement
           The  AWK  versions  of the printf statement and sprintf() function (see
           below) accept the following conversion specification formats:
    
           %c      An ASCII character.  If the argument used for %c is numeric, it
                   is treated as a character and printed.  Otherwise, the argument
                   is assumed to be a string, and the only first character of that
                   string is printed.
    
           %d, %i  A decimal number (the integer part).
    
           %e, %E  A floating point number of the form [-]d.dddddde[+-]dd.  The %E
                   format uses E instead of e.
    
           %f, %F  A floating point number of the form [-]ddd.dddddd.  If the sys-
                   tem  library supports it, %F is available as well. This is like
                   %f, but uses capital letters for special  "not  a  number"  and
                   "infinity" values. If %F is not available, gawk uses %f.
    
           %g, %G  Use %e or %f conversion, whichever is shorter, with nonsignifi-
                   cant zeros suppressed.  The %G format uses %E instead of %e.
    
           %o      An unsigned octal number (also an integer).
    
           %u      An unsigned decimal number (again, an integer).
    
           %s      A character string.
    
           %x, %X  An unsigned hexadecimal number (an  integer).   The  %X  format
                   uses ABCDEF instead of abcdef.
    
           %%      A single % character; no argument is converted.
    
           NOTE: When using the integer format-control letters for values that are
           outside the range of a C long integer, gawk switches to the %0f  format
           specifier.  If  --lint is provided on the command line gawk warns about
           this.  Other versions of awk may print invalid values or  do  something
           else entirely.
    
           Optional,  additional  parameters may lie between the % and the control
           letter:
    
           count$ Use the count'th argument at this point in the formatting.  This
                  is  called  a positional specifier and is intended primarily for
                  supply a leading zero.  For %x, and %X, supply a leading  0x  or
                  0X  for  a  nonzero  result.   For %e, %E, %f and %F, the result
                  always contains a decimal point.  For %g, and %G, trailing zeros
                  are not removed from the result.
    
           0      A  leading 0 (zero) acts as a flag, that indicates output should
                  be padded with zeroes instead of spaces.  This applies  even  to
                  non-numeric  output  formats.  This flag only has an effect when
                  the field width is wider than the value to be printed.
    
           width  The field should be padded to this width.  The field is normally
                  padded  with  spaces.  If the 0 flag has been used, it is padded
                  with zeroes.
    
           .prec  A number that specifies the precision to use when printing.  For
                  the  %e,  %E,  %f  and %F, formats, this specifies the number of
                  digits you want printed to the right of the decimal point.   For
                  the  %g, and %G formats, it specifies the maximum number of sig-
                  nificant digits.  For the %d, %o, %i, %u, %x, and %X formats, it
                  specifies  the  minimum  number  of digits to print.  For %s, it
                  specifies the maximum number of characters from the string  that
                  should be printed.
    
           The dynamic width and prec capabilities of the ANSI C printf() routines
           are supported.  A * in place of either the width or prec specifications
           causes  their  values  to  be taken from the argument list to printf or
           sprintf().  To use a positional specifier with a dynamic width or  pre-
           cision,  supply the count$ after the * in the format string.  For exam-
           ple, "%3$*2$.*1$s".
    
       Special File Names
           When doing I/O redirection from either print or printf into a file,  or
           via  getline  from  a  file,  gawk recognizes certain special filenames
           internally.  These filenames allow  access  to  open  file  descriptors
           inherited  from  gawk's parent process (usually the shell).  These file
           names may also be used on the command line to  name  data  files.   The
           filenames are:
    
           /dev/stdin  The standard input.
    
           /dev/stdout The standard output.
    
           /dev/stderr The standard error output.
    
           /dev/fd/n   The file associated with the open file descriptor n.
    
           These are particularly useful for error messages.  For example:
    
                  print "You blew it!" > "/dev/stderr"
    
           whereas you would otherwise have to use
    
           Other special filenames provide access to information about the running
           gawk  process.   These  filenames  are  now obsolete.  Use the PROCINFO
           array to obtain the information they provide.  The filenames are:
    
           /dev/pid    Reading this file returns the process  ID  of  the  current
                       process, in decimal, terminated with a newline.
    
           /dev/ppid   Reading this file returns the parent process ID of the cur-
                       rent process, in decimal, terminated with a newline.
    
           /dev/pgrpid Reading this file returns the process group ID of the  cur-
                       rent process, in decimal, terminated with a newline.
    
           /dev/user   Reading this file returns a single record terminated with a
                       newline.  The fields are separated with spaces.  $1 is  the
                       value  of the getuid(2) system call, $2 is the value of the
                       geteuid(2) system call, $3 is the value  of  the  getgid(2)
                       system  call,  and $4 is the value of the getegid(2) system
                       call.  If there are any additional  fields,  they  are  the
                       group  IDs  returned  by getgroups(2).  Multiple groups may
                       not be supported on all systems.
    
       Numeric Functions
           AWK has the following built-in arithmetic functions:
    
           atan2(y, x)   Returns the arctangent of y/x in radians.
    
           cos(expr)     Returns the cosine of expr, which is in radians.
    
           exp(expr)     The exponential function.
    
           int(expr)     Truncates to integer.
    
           log(expr)     The natural logarithm function.
    
           rand()        Returns a random number N, between 0 and 1, such that 0 <=
                         N < 1.
    
           sin(expr)     Returns the sine of expr, which is in radians.
    
           sqrt(expr)    The square root function.
    
           srand([expr]) Uses  expr as a new seed for the random number generator.
                         If no expr is provided, the time of  day  is  used.   The
                         return  value  is the previous seed for the random number
                         generator.
    
       String Functions
           Gawk has the following built-in string functions:
    
                                   the array is indexed numerically, and the  val-
                                   ues  are  those  of  the original indices.  The
                                   original values are lost; thus provide a second
                                   array if you wish to preserve the original.
    
           gensub(r, s, h [, t])   Search  the  target string t for matches of the
                                   regular  expression  r.   If  h  is  a   string
                                   beginning with g or G, then replace all matches
                                   of r with s.  Otherwise, h is a number indicat-
                                   ing  which  match of r to replace.  If t is not
                                   supplied,  $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  indicate
                                   just  the  text that matched the n'th parenthe-
                                   sized subexpression.  The  sequence  \0  repre-
                                   sents  the  entire  matched  text,  as does the
                                   character &.  Unlike sub() and gsub(), the mod-
                                   ified  string  is returned as the result of the
                                   function, and the original target string is not
                                   changed.
    
           gsub(r, s [, t])        For each substring matching the regular expres-
                                   sion r in the string t, substitute  the  string
                                   s,  and return the number of substitutions.  If
                                   t is  not  supplied,  use  $0.   An  &  in  the
                                   replacement text is replaced with the text that
                                   was actually matched.  Use \& to get a  literal
                                   &.   (This  must  be  typed as "\\&"; see GAWK:
                                   Effective AWK Programming for a fuller  discus-
                                   sion  of  the  rules for &'s and backslashes in
                                   the replacement text of sub(), gsub(), and gen-
                                   sub().)
    
           index(s, t)             Returns the index of the string t in the string
                                   s, or 0 if t is  not  present.   (This  implies
                                   that character indices start at one.)
    
           length([s])             Returns  the  length  of  the  string s, or the
                                   length of $0 if s is  not  supplied.   Starting
                                   with  version  3.1.5,  as a non-standard exten-
                                   sion, with an array argument, length()  returns
                                   the number of elements in the array.
    
           match(s, r [, a])       Returns  the  position  in  s where the regular
                                   expression r occurs, or 0 if r is not  present,
                                   and  sets  the  values  of  RSTART and RLENGTH.
                                   Note that the argument order is the same as for
                                   the  ~  operator: str ~ re.  If array a is pro-
                                   vided, a is cleared and then elements 1 through
                                   n  are filled with the portions of s that match
                                   the corresponding  parenthesized  subexpression
                                   in  r.  The 0'th element of a contains the por-
                                   the resulting string.
    
           strtonum(str)           Examines str, and returns  its  numeric  value.
                                   If  str  begins  with  a  leading 0, strtonum()
                                   assumes that str is an octal  number.   If  str
                                   begins  with  a  leading  0x  or 0X, strtonum()
                                   assumes that str is a hexadecimal number.
    
           sub(r, s [, t])         Just like gsub(), but only the  first  matching
                                   substring is replaced.
    
           substr(s, i [, n])      Returns  the at most n-character substring of s
                                   starting at i.  If n is omitted, the rest of  s
                                   is used.
    
           tolower(str)            Returns  a copy of the string str, with all the
                                   upper-case  characters  in  str  translated  to
                                   their  corresponding  lower-case  counterparts.
                                   Non-alphabetic characters are left unchanged.
    
           toupper(str)            Returns a copy of the string str, with all  the
                                   lower-case  characters  in  str  translated  to
                                   their  corresponding  upper-case  counterparts.
                                   Non-alphabetic characters are left unchanged.
    
           As of version 3.1.5, gawk is multibyte aware.  This means that index(),
           length(), substr() and match() all work in  terms  of  characters,  not
           bytes.
    
       Time Functions
           Since  one  of the primary uses of AWK programs is processing log files
           that contain time stamp information, gawk provides the following  func-
           tions for obtaining time stamps and formatting them.
    
           mktime(datespec)
                     Turns datespec into a time stamp of the same form as returned
                     by systime().  The datespec is a string of the form  YYYY  MM
                     DD  HH  MM  SS[  DST].  The contents of the string are six or
                     seven numbers representing respectively the full year includ-
                     ing  century,  the  month  from 1 to 12, the day of the month
                     from 1 to 31, the hour of the day from 0 to  23,  the  minute
                     from  0  to  59, and the second from 0 to 60, and an optional
                     daylight saving flag.  The values of these numbers  need  not
                     be  within  the  ranges specified; for example, an hour of -1
                     means 1 hour before midnight.  The origin-zero Gregorian cal-
                     endar  is  assumed,  with year 0 preceding year 1 and year -1
                     preceding year 0.  The time is assumed to  be  in  the  local
                     timezone.   If the daylight saving flag is positive, the time
                     is assumed to be daylight saving time; if zero, the  time  is
                     assumed  to  be standard time; and if negative (the default),
                     mktime() attempts to determine whether daylight  saving  time
    
           systime() Returns  the  current  time  of  day as the number of seconds
                     since the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).
    
       Bit Manipulations Functions
           Starting with version 3.1 of gawk, the following bit manipulation func-
           tions are available.  They work by converting double-precision floating
           point values to uintmax_t integers, doing the operation, and then  con-
           verting the result back to floating point.  The functions are:
    
           and(v1, v2)         Return the bitwise AND of the values provided by v1
                               and v2.
    
           compl(val)          Return the bitwise complement of val.
    
           lshift(val, count)  Return the value of  val,  shifted  left  by  count
                               bits.
    
           or(v1, v2)          Return  the bitwise OR of the values provided by v1
                               and v2.
    
           rshift(val, count)  Return the value of val,  shifted  right  by  count
                               bits.
    
           xor(v1, v2)         Return the bitwise XOR of the values provided by v1
                               and v2.
    
       Internationalization Functions
           Starting with version 3.1 of gawk, the following functions may be  used
           from  within your AWK program for translating strings at run-time.  For
           full details, see GAWK: Effective AWK Programming.
    
           bindtextdomain(directory [, domain])
                  Specifies the directory where gawk looks for the .mo  files,  in
                  case they will not or cannot be placed in the ''standard'' loca-
                  tions (e.g., during testing).  It returns  the  directory  where
                  domain is ''bound.''
                  The  default domain is the value of TEXTDOMAIN.  If directory is
                  the null string (""), then bindtextdomain() returns the  current
                  binding for the given domain.
    
           dcgettext(string [, domain [, category]])
                  Returns  the  translation  of  string  in text domain domain for
                  locale category category.  The default value for domain  is  the
                  current  value of TEXTDOMAIN.  The default value for category is
                  "LC_MESSAGES".
                  If you supply a value for category, it must be a string equal to
                  one  of the known locale categories described in GAWK: Effective
                  AWK Programming.  You must  also  supply  a  text  domain.   Use
                  TEXTDOMAIN if you want to use the current domain.
    
    
           Functions  are executed when they are called from within expressions in
           either patterns or actions.  Actual parameters supplied in the function
           call  are  used  to  instantiate  the formal parameters declared in the
           function.  Arrays are passed by reference, other variables  are  passed
           by value.
    
           Since  functions were not originally part of the AWK language, the pro-
           vision for local variables is rather clumsy: They are declared as extra
           parameters  in the parameter list.  The convention is to separate local
           variables from real parameters by extra spaces in the  parameter  list.
           For example:
    
                  function  f(p, q,     a, b)   # a and b are local
                  {
                       ...
                  }
    
                  /abc/     { ... ; f(1, 2) ; ... }
    
           The left parenthesis in a function call is required to immediately fol-
           low the function name,  without  any  intervening  white  space.   This
           avoids  a  syntactic  ambiguity  with the concatenation operator.  This
           restriction does not apply to the built-in functions listed above.
    
           Functions may call each other and may be recursive.   Function  parame-
           ters used as local variables are initialized to the null string and the
           number zero upon function invocation.
    
           Use return expr to return a value from a function.  The return value is
           undefined  if  no  value  is  provided,  or  if the function returns by
           "falling off" the end.
    
           If --lint has been provided, gawk warns about calls to undefined  func-
           tions  at  parse  time,  instead  of at run time.  Calling an undefined
           function at run time is a fatal error.
    
           The word func may be used in place of function.
    
    
    

    DYNAMICALLY LOADING NEW FUNCTIONS

           Beginning with version 3.1 of gawk, you can dynamically add new  built-
           in  functions  to  the  running gawk interpreter.  The full details are
           beyond the scope of this manual page; see GAWK: Effective AWK  Program-
           ming for the details.
    
           extension(object, function)
                   Dynamically  link  the  shared object file named by object, and
                   invoke function in  that  object,  to  perform  initialization.
                   These  should  both  be provided as strings.  Returns the value
                   returned by function.
    
    
                BEGIN     { FS = ":" }
                     { print $1 | "sort" }
    
           Count lines in a file:
    
                     { nlines++ }
                END  { print nlines }
    
           Precede each line by its number in the file:
    
                { print FNR, $0 }
    
           Concatenate and line number (a variation on a theme):
    
                { print NR, $0 }
           Run an external command for particular lines of data:
    
                tail -f access_log |
                awk '/myhome.html/ { system("nmap " $1 ">> logdir/myhome.html") }'
    
    
    

    INTERNATIONALIZATION

           String constants are sequences of characters enclosed in double quotes.
           In non-English speaking environments, it is possible to mark strings in
           the  AWK  program  as  requiring translation to the native natural lan-
           guage. Such strings are marked in the AWK program with a leading under-
           score ("_").  For example,
    
                  gawk 'BEGIN { print "hello, world" }'
    
           always prints hello, world.  But,
    
                  gawk 'BEGIN { print _"hello, world" }'
    
           might print bonjour, monde in France.
    
           There are several steps involved in producing and running a localizable
           AWK program.
    
           1.  Add a BEGIN action to assign a value to the TEXTDOMAIN variable  to
               set the text domain to a name associated with your program.
    
               BEGIN { TEXTDOMAIN = "myprog" }
    
           This  allows  gawk  to  find the .mo file associated with your program.
           Without this step, gawk uses the messages  text  domain,  which  likely
           does not contain translations for your program.
    
           2.  Mark  all  strings  that  should  be translated with leading under-
               scores.
    
           3.  If necessary, use the dcgettext() and/or bindtextdomain() functions
           porates the following user visible features which are not described  in
           the AWK book, but are part of the Bell Laboratories version of awk, and
           are in the POSIX standard.
    
           The book indicates that command line variable assignment  happens  when
           awk  would  otherwise  open  the argument as a file, which is after the
           BEGIN block is executed.  However,  in  earlier  implementations,  when
           such an assignment appeared before any file names, the assignment would
           happen before the BEGIN block was run.  Applications came to depend  on
           this  "feature."   When awk was changed to match its documentation, the
           -v option for assigning variables before program execution was added to
           accommodate  applications  that  depended upon the old behavior.  (This
           feature was agreed upon by both  the  Bell  Laboratories  and  the  GNU
           developers.)
    
           The  -W  option  for implementation specific features is from the POSIX
           standard.
    
           When processing arguments, gawk uses the special option "--" to  signal
           the end of arguments.  In compatibility mode, it warns about but other-
           wise ignores undefined options.  In normal  operation,  such  arguments
           are passed on to the AWK program for it to process.
    
           The  AWK  book  does not define the return value of srand().  The POSIX
           standard has it return the seed it was using, to allow keeping track of
           random  number  sequences.   Therefore srand() in gawk also returns its
           current seed.
    
           Other new features are: The use of multiple -f options (from MKS  awk);
           the  ENVIRON array; the \a, and \v escape sequences (done originally in
           gawk and fed back into the Bell Laboratories  version);  the  tolower()
           and  toupper() built-in functions (from the Bell Laboratories version);
           and the ANSI C conversion specifications in printf (done first  in  the
           Bell Laboratories version).
    
    
    

    HISTORICAL FEATURES

           There are two features of historical AWK implementations that gawk sup-
           ports.  First, it is possible to call the  length()  built-in  function
           not only with no argument, but even without parentheses!  Thus,
    
                  a = length     # Holy Algol 60, Batman!
    
           is the same as either of
    
                  a = length()
                  a = length($0)
    
           This  feature is marked as "deprecated" in the POSIX standard, and gawk
           issues a warning about its use if --lint is specified  on  the  command
           line.
    
           The other feature is the use of either the continue or the break state-
    
           ? The \x escape sequence.  (Disabled with --posix.)
    
           ? The fflush() function.  (Disabled with --posix.)
    
           ? The ability to  continue  lines  after  ?   and  :.   (Disabled  with
             --posix.)
    
           ? Octal and hexadecimal constants in AWK programs.
    
           ? The ARGIND, BINMODE, ERRNO, LINT, RT and TEXTDOMAIN variables are not
             special.
    
           ? The IGNORECASE variable and its side-effects are not available.
    
           ? The FIELDWIDTHS variable and fixed-width field splitting.
    
           ? The PROCINFO array is not available.
    
           ? The use of RS as a regular expression.
    
           ? The special file names available for I/O redirection are  not  recog-
             nized.
    
           ? The |& operator for creating co-processes.
    
           ? The  ability to split out individual characters using the null string
             as the value of FS, and as the third argument to split().
    
           ? The optional second argument to the close() function.
    
           ? The optional third argument to the match() function.
    
           ? The ability to use positional specifiers with printf and sprintf().
    
           ? The ability to pass an array to length().
    
           ? The use of delete array to delete the entire contents of an array.
    
           ? The use of nextfile to abandon processing of the current input  file.
    
           ? The and(), asort(), asorti(), bindtextdomain(), compl(), dcgettext(),
             dcngettext(), gensub(), lshift(),  mktime(),  or(),  rshift(),  strf-
             time(), strtonum(), systime() and xor() functions.
    
           ? Localizable strings.
    
           ? Adding  new built-in functions dynamically with the extension() func-
             tion.
    
           The AWK book does not define the return value of the close()  function.
           Gawk's  close()  returns  the  value from fclose(3), or pclose(3), when
           command, then it accepts an additional control-flow statement:
                  switch (expression) {
                  case value|regex : statement
                  ...
                  [ default: statement ]
                  }
    
           If gawk is configured with the --disable-directories-fatal option, then
           it  will  silently  skip directories named on the command line.  Other-
           wise, it will do so only if invoked with the --traditional option.
    
    
    

    ENVIRONMENT VARIABLES

           The AWKPATH environment variable can be  used  to  provide  a  list  of
           directories  that gawk searches when looking for files named via the -f
           and --file options.
    
           If POSIXLY_CORRECT exists in the environment, then gawk behaves exactly
           as  if  --posix  had been specified on the command line.  If --lint has
           been specified, gawk issues a warning message to this effect.
    
    
    

    SEE ALSO

           egrep(1), getpid(2),  getppid(2),  getpgrp(2),  getuid(2),  geteuid(2),
           getgid(2), getegid(2), getgroups(2)
    
           The  AWK Programming Language, Alfred V. Aho, Brian W. Kernighan, Peter
           J. Weinberger, Addison-Wesley, 1988.  ISBN 0-201-07981-X.
    
           GAWK: Effective AWK Programming, Edition 3.0,  published  by  the  Free
           Software  Foundation,  2001.   The  current version of this document is
           available online at http://www.gnu.org/software/gawk/manual.
    
    
    

    BUGS

           The -F option is not necessary given the command line variable  assign-
           ment feature; it remains only for backwards compatibility.
    
           Syntactically  invalid  single  character programs tend to overflow the
           parse stack, generating a rather unhelpful message.  Such programs  are
           surprisingly  difficult to diagnose in the completely general case, and
           the effort to do so really is not worth it.
    
    
    

    AUTHORS

           The original version of UNIX awk was designed and implemented by Alfred
           Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories.  Brian
           Kernighan continues to maintain and enhance it.
    
           Paul Rubin and Jay Fenlason, of the  Free  Software  Foundation,  wrote
           gawk,  to be compatible with the original version of awk distributed in
           Seventh Edition UNIX.  John Woods contributed a number  of  bug  fixes.
           David  Trueman,  with contributions from Arnold Robbins, made gawk com-
           patible with the new version of UNIX awk.  Arnold Robbins is  the  cur-
           rent maintainer.
    
           This man page documents gawk, version 3.1.7.
    
    
    

    BUG REPORTS

           If you find a  bug  in  gawk,  please  send  electronic  mail  to  bug-
           gawk@gnu.org.   Please  include your operating system and its revision,
           the version of gawk (from gawk --version), what C compiler you used  to
           compile  it,  and a test program and data that are as small as possible
           for reproducing the problem.
    
           Before sending a bug report, please do the  following  things.   First,
           verify  that  you  have the latest version of gawk.  Many bugs (usually
           subtle ones) are fixed at each release, and if yours is  out  of  date,
           the  problem  may already have been solved.  Second, please see if set-
           ting the environment variable  LC_ALL  to  LC_ALL=C  causes  things  to
           behave  as  you  expect. If so, it's a locale issue, and may or may not
           really be a bug.  Finally, please read this man page and the  reference
           manual  carefully  to  be  sure that what you think is a bug really is,
           instead of just a quirk in the language.
    
           Whatever you do, do NOT post a bug report in comp.lang.awk.  While  the
           gawk  developers  occasionally read this newsgroup, posting bug reports
           there is an unreliable way to report bugs.   Instead,  please  use  the
           electronic mail addresses given above.
    
           If you're using a GNU/Linux system or BSD-based system, you may wish to
           submit a bug report to the vendor of your distribution.   That's  fine,
           but  please  send  a  copy to the official email address as well, since
           there's no guarantee that the bug will be forwarded to the  gawk  main-
           tainer.
    
    
    

    ACKNOWLEDGEMENTS

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

    COPYING PERMISSIONS

           Copyright (C) 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
           2001, 2002, 2003, 2004, 2005, 2007, 2009 Free Software Foundation, Inc.
    
           Permission is granted to make and distribute verbatim  copies  of  this
           manual  page  provided  the copyright notice and this permission notice
           are preserved on all copies.
    
           Permission is granted to copy and distribute modified versions of  this
           manual  page  under  the conditions for verbatim copying, provided that
           the entire resulting derived work is distributed under the terms  of  a
           permission notice identical to this one.
    
           Permission  is granted to copy and distribute translations of this man-
           ual page into another language, under the above conditions for modified
           versions,  except that this permission notice may be stated in a trans-
           lation approved by the Foundation.
    
    
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