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GAWK(1)                                            Utility Commands                                           GAWK(1)



NAME
       gawk - pattern scanning and processing language

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

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

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

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

       The command line consists of options to gawk itself, the AWK program text (if  not  supplied  via  the  -f  or
       --file options), and values to be made available in the ARGC and ARGV pre-defined AWK variables.

       Pgawk  is  the profiling version of gawk.  It is identical in every way to gawk, except that programs run more
       slowly, and it automatically produces an execution profile in the file awkprof.out when done.  See the  --pro‐
       file option, below.

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

OPTION FORMAT
       Gawk  options  may  be  either  traditional  POSIX-style one letter options, or GNU-style long options.  POSIX
       options start with a single “-”, while long options start with “--”.  Long options are provided for both  GNU-
       specific features and for POSIX-mandated features.

       Gawk-  specific  options  are typically used in long-option form.  Arguments to long options are either joined
       with the option by an = sign, with no intervening spaces, or they may be provided in  the  next  command  line
       argument.  Long options may be abbreviated, as long as the abbreviation remains unique.

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

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

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

       -F fs
       --field-separator fs
              Use fs for the input field separator (the value of the FS predefined variable).

       -v var=val
       --assign var=val

              GNU-specific extensions are recognized.  See GNU EXTENSIONS, below, for more information.

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

       -d[file]
       --dump-variables[=file]
              Print a sorted list of global variables, their types and final values to file.  If no file is provided,
              gawk uses a file named awkvars.out in the current directory.
              Having a list of all the global variables is a good way to look for typographical errors in  your  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 inadvertently use global  variables  that  you  meant  to  be
              local.  (This is a particularly easy mistake to make with simple variable names like i, j, and so on.)

       -e program-text
       --source program-text
              Use  program-text as AWK program source code.  This option allows the easy intermixing of library 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.

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

       -g
       --gen-pot
              Scan and parse the AWK program, and generate a GNU .pot (Portable Object Template) format file on stan‐
              dard output with entries for all localizable strings in the program.  The program itself  is  not  exe‐
              cuted.  See the GNU gettext distribution for more information on .pot files.

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

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

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

       -N
       --use-lc-numeric
              This forces gawk to use the locale's decimal point character when parsing  input  data.   Although  the
              POSIX  standard  requires  this behavior, and gawk does so when --posix is in effect, the default is to
              a “pretty printed” version of the program.  When run with pgawk, the profile contains execution  counts
              of  each  statement  in  the  program in the left margin and function call counts for each user-defined
              function.

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

              · \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 ^=.

       -r
       --re-interval
              Enable the use of interval expressions in regular expression matching (see Regular Expressions, below).
              Interval  expressions  were  not traditionally available in the AWK language.  The POSIX standard added
              them, to make awk and egrep consistent with each other.  They are enabled by default, but  this  option
              remains for use with --traditional.

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

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

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

       -V
       --version
              Print version information for this particular copy of gawk on the  standard  output.   This  is  useful
              mainly  for  knowing  if the current copy of gawk on your system is up to date with respect to whatever
              the Free Software Foundation is distributing.  This is also useful when reporting bugs.  (Per  the  GNU
              Coding Standards, these options cause an immediate, successful exit.)

       --     Signal the end of options. This is useful to allow further arguments to the AWK program itself to start
              with a “-”.  This provides consistency with the argument parsing convention used by  most  other  POSIX
              programs.

       In  compatibility mode, any other options are flagged as invalid, but are otherwise ignored.  In normal opera‐
       tion, 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 inter‐
       them in each new AWK program that uses them.  It also provides the ability to mix library functions with  com‐
       mand line programs.

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

       The environment variable AWKPATH specifies a search path to use when finding source files named  with  the  -f
       option.  If this variable does not exist, the default path is ".:/usr/local/share/awk".  (The actual directory
       may vary, depending upon how gawk was built and installed.)  If a file name given to the -f option contains  a
       “/” character, no path search is performed.

       Gawk  executes  AWK  programs  in  the  following order.  First, all variable assignments specified via the -v
       option are performed.  Next, gawk compiles the program into an internal form.  Then, gawk executes the code in
       the  BEGIN  block(s) (if any), and then proceeds to read each file named in the ARGV array (up to ARGV[ARGC]).
       If there are no files named on the command line, gawk reads the standard input.

       If a filename on the command line has the form var=val it is treated as a variable assignment.   The  variable
       var  will  be  assigned  the  value val.  (This happens after any BEGIN block(s) have been run.)  Command line
       variable assignment is most useful for dynamically assigning values to the variables AWK uses to  control  how
       input  is  broken  into  fields  and  records.  It is also useful for controlling state if multiple passes are
       needed over a single data file.

       If the value of a particular element of ARGV is empty (""), gawk skips over it.

       For each input file, if a BEGINFILE rule exists, gawk executes the associated code before processing the  con‐
       tents of the file. Similarly, gawk executes the code associated with ENDFILE after processing the file.

       For  each  record in the input, gawk tests to see if it matches any pattern in the AWK program.  For each pat‐
       tern that the record matches, the associated action is executed.  The patterns are tested in  the  order  they
       occur in the program.

       Finally, after all the input is exhausted, gawk executes the code in the END block(s) (if any).

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

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

VARIABLES, RECORDS AND FIELDS
       AWK variables are dynamic; they come into existence when they are first used.  Their values are either  float‐
       ing-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.   Other‐
       wise,  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 newline character always acts as a field separator, in addition  to  whatever  value  FS  may
       width, and gawk splits up the record using the specified widths.  The value of FS is ignored.  Assigning a new
       value to FS or FPAT overrides the use of FIELDWIDTHS.

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

       Each field in the input record may be referenced by its position, $1, $2, and so on.  $0 is the whole  record.
       Fields need not be referenced by constants:

              n = 5
              print $n

       prints the fifth field in the input record.

       The variable NF is set to the total number of fields in the input record.

       References  to  non-existent  fields (i.e. fields after $NF) produce the null-string.  However, assigning to a
       non-existent field (e.g., $(NF+2) = 5) increases the value of NF, creates any intervening fields with the null
       string  as  their  value,  and causes the value of $0 to be recomputed, with the fields being separated by the
       value of OFS.  References to negative numbered fields cause a fatal error.  Decrementing NF causes the  values
       of fields past the new value to be lost, and the value of $0 to be recomputed, with the fields being separated
       by the value of OFS.

       Assigning a value to an existing field causes the whole record to be rebuilt when  $0  is  referenced.   Simi‐
       larly, assigning a value to $0 causes the record to be resplit, creating new values for the fields.

   Built-in Variables
       Gawk's built-in variables are:

       ARGC        The number of command line arguments (does not include options to gawk, or the program source).

       ARGIND      The index in ARGV of the current file being processed.

       ARGV        Array  of  command line arguments.  The array is indexed from 0 to ARGC - 1.  Dynamically changing
                   the contents of ARGV can control the files used for data.

       BINMODE     On non-POSIX systems, specifies use of “binary” mode for all file I/O.  Numeric values of 1, 2, or
                   3,  specify  that  input  files,  output files, or all files, respectively, should use binary I/O.
                   String values of "r", or "w" specify that input files, or output files, respectively,  should  use
                   binary  I/O.   String  values  of  "rw" or "wr" specify that all files should use binary I/O.  Any
                   other string value is treated as "rw", but generates a warning 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  environ‐
                   ment  variables,  each  element  being  the value of that variable (e.g., ENVIRON["HOME"] might be
                   /home/arnold).  Changing this array does not affect the environment seen by  programs  which  gawk
                   spawns via 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.

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

       IGNORECASE  Controls  the case-sensitivity of all regular expression and string operations.  If IGNORECASE has
                   a non-zero value, then string comparisons and pattern matching in rules, field splitting  with  FS
                   and  FPAT, record separating with RS, regular expression matching with ~ and !~, and the gensub(),
                   gsub(), index(), match(), patsplit(), split(), and sub() built-in functions all ignore  case  when
                   doing  regular  expression  operations.   NOTE:  Array subscripting is not affected.  However, the
                   asort() and asorti() functions are affected.
                   Thus, if IGNORECASE is not equal to zero, /aB/ matches all of the strings "ab",  "aB",  "Ab",  and
                   "AB".   As with all AWK variables, the initial value of IGNORECASE is zero, so all regular expres‐
                   sion and string operations are normally case-sensitive.

       LINT        Provides dynamic control of the --lint option from within an AWK program.  When true, gawk  prints
                   lint  warnings.  When  false,  it does not.  When assigned the string value "fatal", lint warnings
                   become fatal errors, exactly like --lint=fatal.  Any other true value just prints warnings.

       NF          The number of fields in the current input record.

       NR          The total number of input records seen so far.

       OFMT        The output format for numbers, "%.6g", by default.

       OFS         The output field separator, a space by default.

       ORS         The output record separator, by default a newline.

       PROCINFO    The elements of this array provide access to information about the running AWK program.   On  some
                   systems,  there  may  be elements in the array, "group1" through "groupn" for some n, which is the
                   number of supplementary groups that the process has.  Use the in operator to test for  these  ele‐
                   ments.  The following elements are guaranteed to be available:

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

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

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

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

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

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

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

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

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

                   PROCINFO["sorted_in"]

                   PROCINFO["version"]
                          the version of gawk.

       RS          The input record separator, by default a newline.

       RT          The record terminator.  Gawk sets RT to the input text  that  matched  the  character  or  regular
                   expression specified by RS.

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

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

       SUBSEP      The character used to separate multiple subscripts in array elements, by default "\034".

       TEXTDOMAIN  The text domain of the AWK program; used to find the  localized  translations  for  the  program's
                   strings.

   Arrays
       Arrays  are subscripted with an expression between square brackets ([ and ]).  If the expression is an expres‐
       sion list (expr, expr ...)  then the array subscript is a  string  consisting  of  the  concatenation  of  the
       (string)  value  of  each expression, separated by the value of the SUBSEP variable.  This facility is used to
       simulate multiply dimensioned arrays.  For example:

              i = "A"; j = "B"; k = "C"
              x[i, j, k] = "hello, world\n"

       assigns the string "hello,  world\n"  to  the  element  of  the  array  x  which  is  indexed  by  the  string
       "A\034B\034C".  All arrays in AWK are associative, i.e. indexed by string values.

       The special operator in may be used to test if an array has an index consisting of a particular value:

              if (val in array)
                   print array[val]

       If the array has multiple subscripts, use (i, j) in array.

       The in construct may also be used in a for loop to iterate over all the elements of an array.

       An  element may be deleted from an array using the delete statement.  The delete statement may also be used to
       delete the entire contents of an array, just by specifying the array name without a subscript.

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

   Variable Typing And Conversion
       Variables  and  fields  may  be (floating point) numbers, or strings, or both.  How the value of a variable is
       interpreted depends upon its 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.

       the variable b has a string value of "12" and not "12.00".

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

       Gawk  performs  comparisons  as  follows: If two variables are numeric, they are compared numerically.  If one
       value is numeric and the other has a string value that is a “numeric string,” then comparisons are  also  done
       numerically.  Otherwise, the numeric value is converted to a string and a string comparison is performed.  Two
       strings are compared, of course, as strings.

       Note that string constants, such as "57", are not numeric strings, they are string  constants.   The  idea  of
       “numeric string” only applies to fields, getline input, FILENAME, ARGV elements, ENVIRON elements and the ele‐
       ments of an array created by split() or patsplit() that are numeric strings.  The  basic  idea  is  that  user
       input, and only user input, that looks numeric, should be treated that way.

       Uninitialized variables have the numeric value 0 and the string value "" (the null, or empty, string).

   Octal and Hexadecimal Constants
       You  may  use C-style octal and hexadecimal constants in your AWK program source code.  For example, the octal
       value 011 is equal to decimal 9, and the hexadecimal value 0x11 is equal to decimal 17.

   String Constants
       String constants in AWK are sequences of characters enclosed between double  quotes  (like  "value").   Within
       strings, certain escape sequences are recognized, as in C.  These are:

       \\   A literal backslash.

       \a   The “alert” character; usually the ASCII BEL character.

       \b   backspace.

       \f   form-feed.

       \n   newline.

       \r   carriage return.

       \t   horizontal tab.

       \v   vertical tab.

       \xhex digits
            The  character  represented by the string of hexadecimal digits 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  regular  expressions  (e.g.,  /[ \t\f\n\r\v]/  matches
       whitespace characters).
       which prints the entire record.

       Comments begin with the # character, and continue until the end of the line.  Blank lines may be used to sepa‐
       rate statements.  Normally, a statement ends with a newline, however, this is not the case for lines ending in
       a comma, {, ?, :, &&, or ||.  Lines ending in do or else also have their statements automatically continued on
       the following line.  In other cases, a line can be continued by ending it with a “\”, in which case  the  new‐
       line is ignored.

       Multiple statements may be put on one line by separating them with a “;”.  This applies to both the statements
       within the action part of a pattern-action pair (the usual case), and to the pattern-action  statements  them‐
       selves.

   Patterns
       AWK patterns may be one of the following:

              BEGIN
              END
              BEGINFILE
              ENDFILE
              /regular expression/
              relational expression
              pattern && pattern
              pattern || pattern
              pattern ? pattern : pattern
              (pattern)
              ! pattern
              pattern1, pattern2

       BEGIN  and  END are two special kinds of patterns which are not tested against the input.  The action parts of
       all BEGIN patterns are merged as if all the statements had been written in a single  BEGIN  block.   They  are
       executed before any of the input is read.  Similarly, all the END blocks are merged, and executed when all the
       input is exhausted (or when an exit statement is executed).  BEGIN and END patterns cannot  be  combined  with
       other patterns in pattern expressions.  BEGIN and END patterns cannot have missing action parts.

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

       For /regular expression/ patterns, the associated statement is executed for each input record that matches the
       regular expression.  Regular expressions are the same as those in egrep(1), and are summarized below.

       A relational expression may use any of the operators defined below in the section on actions.  These generally
       test whether certain fields match certain regular expressions.

       The  &&,  ||,  and  !  operators are logical AND, logical OR, and logical NOT, respectively, as in C.  They do
       short-circuit evaluation, also as in C, and are used for combining more primitive pattern expressions.  As  in
       most languages, parentheses may be used to change the order of evaluation.

       The  ?: operator is like the same operator in C.  If the first pattern is true then the pattern used for test‐
       ing 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
       ^          matches the beginning of a string.

       $          matches the end of a string.

       [abc...]   character list, matches any of the characters abc....

       [^abc...]  negated character list, matches any character except abc....

       r1|r2      alternation: matches either r1 or r2.

       r1r2       concatenation: matches r1, and then r2.

       r+         matches one or more r's.

       r*         matches zero or more r's.

       r?         matches zero or one r's.

       (r)        grouping: matches r.

       r{n}
       r{n,}
       r{n,m}     One or two numbers inside braces denote an interval expression.  If there  is  one  number  in  the
                  braces, the preceding regular expression r is repeated n times.  If there are two numbers separated
                  by a comma, r is repeated n to m times.  If there is one number followed by  a  comma,  then  r  is
                  repeated at least n times.

       \y         matches the empty string at either the beginning or the end of a word.

       \B         matches the empty string within a word.

       \<         matches the empty string at the beginning of a word.

       \>         matches the empty string at the end of a word.

       \s         matches any whitespace character.

       \S         matches any nonwhitespace character.

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

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

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

       \'         matches the empty string at the end of a buffer.

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

       Character classes are a feature introduced in the POSIX standard.  A character class is a special notation for
       describing lists of characters that have a specific attribute, but where the actual characters themselves  can
       vary  from  country to country and/or from character set to character set.  For example, the notion of what is
       an alphabetic character differs in the USA and in France.

       [:digit:]  Numeric characters.

       [:graph:]  Characters that are both printable and visible.  (A space is printable, but not visible, while an a
                  is both.)

       [:lower:]  Lowercase alphabetic characters.

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

       [:punct:]  Punctuation  characters (characters that are not letter, digits, control characters, or space char‐
                  acters).

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

       [:upper:]  Uppercase alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.

       For example, before the POSIX standard, to  match  alphanumeric  characters,  you  would  have  had  to  write
       /[A-Za-z0-9]/.  If your character set had other alphabetic characters in it, this would not match them, and if
       your character set collated differently from ASCII, this might not even match the ASCII  alphanumeric  charac‐
       ters.   With  the  POSIX  character  classes, you can write /[[:alnum:]]/, and this matches the alphabetic and
       numeric characters in your character set, no matter what it is.

       Two additional special sequences can appear in character lists.  These  apply  to  non-ASCII  character  sets,
       which  can  have single symbols (called collating elements) that are represented with more than one character,
       as well as several characters that are equivalent for collating, or sorting, purposes.  (E.g.,  in  French,  a
       plain “e” and a grave-accented “`” are equivalent.)

       Collating Symbols
              A  collating  symbol is a multi-character collating element enclosed in [.  and .].  For example, if ch
              is a collating element, then [[.ch.]]  is a regular expression that  matches  this  collating  element,
              while [ch] is a regular expression that matches either c or h.

       Equivalence Classes
              An  equivalence class is a locale-specific name for a list of characters that are equivalent.  The name
              is enclosed in [= and =].  For example, the name e might be used to represent all of “e,” “´,” and “`.”
              In this case, [[=e=]] is a regular expression that matches any of e, ´, or `.

       These  features  are  very valuable in non-English speaking locales.  The library functions that gawk uses for
       regular expression matching currently only recognize POSIX character classes; they do not recognize  collating
       symbols or equivalence classes.

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

       The various command line options control how gawk interprets characters in regular expressions.

       No options
              In the default case, gawk provide all the facilities of POSIX regular expressions and the  GNU  regular
              expression operators described above.

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

       tional,  and  looping statements found in most languages.  The operators, control statements, and input/output
       statements available are patterned after those in C.

   Operators
       The operators in AWK, in order of decreasing precedence, are

       (...)       Grouping

       $           Field reference.

       ++ --       Increment and decrement, both prefix and postfix.

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

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

       * / %       Multiplication, division, and modulus.

       + -         Addition and subtraction.

       space       String concatenation.

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

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

       ~ !~        Regular expression match, negated match.  NOTE: Do not use a constant regular  expression  (/foo/)
                   on  the left-hand side of a ~ or !~.  Only use one on the right-hand side.  The expression /foo/ ~
                   exp has the same meaning as (($0 ~ /foo/) ~ exp).  This is usually not what was intended.

       in          Array membership.

       &&          Logical AND.

       ||          Logical OR.

       ?:          The C conditional expression.  This has the form expr1 ? expr2 : expr3.  If  expr1  is  true,  the
                   value  of  the  expression is expr2, otherwise it is expr3.  Only one of expr2 and expr3 is evalu‐
                   ated.

       = += -= *= /= %= ^=
                   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

       The input/output statements are as follows:

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

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

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

       getline var           Set var from next input record; set NR, FNR.

       getline var <file     Set var from next record of file.

       command | getline [var]
                             Run command piping the output either into $0 or var, as above.

       command |& getline [var]
                             Run  command as a co-process piping the output either into $0 or var, as above.  Co-pro‐
                             cesses are a gawk extension.  (command can also be a socket.  See the subsection Special
                             File Names, below.)

       next                  Stop  processing the current input record.  The next input record is read and processing
                             starts over with the first pattern in the AWK program.  If the end of the input data  is
                             reached, the END block(s), if any, are executed.

       nextfile              Stop  processing the current input file.  The next input record read comes from the next
                             input file.  FILENAME and ARGIND are updated, FNR is reset to 1, and  processing  starts
                             over with the first pattern in the AWK program. If the end of the input data is reached,
                             the END block(s), if any, are executed.

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

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

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

       printf fmt, expr-list Format and print.  See The printf Statement, below.

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

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

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

       Additional output redirections are allowed for print and printf.

       print ... >> file
       tion.  If  using a pipe, co-process, or socket to getline, or from print or printf within a loop, you must use
       close() to create new instances of the command or socket.  AWK does not automatically close pipes, sockets, or
       co-processes when they return EOF.

   The printf Statement
       The  AWK  versions  of the printf statement and sprintf() function (see below) accept the following conversion
       specification formats:

       %c      A single character.  If the argument used for %c is numeric, it is treated as a character and printed.
               Otherwise,  the  argument  is  assumed  to be a string, and the only first character of that string is
               printed.

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

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

       %f, %F  A floating point number of the form [-]ddd.dddddd.  If the system library supports it, %F is available
               as  well.  This is like %f, but uses capital letters for special “not a number” and “infinity” values.
               If %F is not available, gawk uses %f.

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

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

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

       %s      A character string.

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

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

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

       count$ Use  the  count'th argument at this point in the formatting.  This is called a positional specifier and
              is intended primarily for use in translated versions of format strings, not in the original text of  an
              AWK program.  It is a gawk extension.

       -      The expression should be left-justified within its field.

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

       +      The  plus  sign,  used  before the width modifier (see below), says to always supply a sign for numeric
              conversions, even if the data to be formatted is positive.  The + overrides the space modifier.

       #      Use an “alternate form” for certain control letters.  For %o, supply a leading zero.  For %x,  and  %X,
              supply  a  leading  0x or 0X for a nonzero result.  For %e, %E, %f and %F, the result always contains a
              decimal point.  For %g, and %G, trailing zeros are not removed from the result.

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


       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  recog‐
       nizes  certain  special filenames internally.  These filenames allow access to open file descriptors inherited
       from gawk's parent process (usually the shell).  These file names may also be used on the command line to name
       data files.  The filenames are:

       /dev/stdin  The standard input.

       /dev/stdout The standard output.

       /dev/stderr The standard error output.

       /dev/fd/n   The file associated with the open file descriptor n.

       These are particularly useful for error messages.  For example:

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

       whereas you would otherwise have to use

              print "You blew it!" | "cat 1>&2"

       The  following  special filenames may be used with the |& co-process operator for creating TCP/IP network con‐
       nections:

       /inet/tcp/lport/rhost/rport
       /inet4/tcp/lport/rhost/rport
       /inet6/tcp/lport/rhost/rport
              Files for a TCP/IP connection on local port lport to remote host rhost on remote  port  rport.   Use  a
              port  of 0 to have the system pick a port.  Use /inet4 to force an IPv4 connection, and /inet6 to force
              an IPv6 connection.  Plain /inet uses the system default (most likely IPv4).

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

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

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

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

       exp(expr)     The exponential function.

       int(expr)     Truncate to integer.

       log(expr)     The natural logarithm function.

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


                               s  with  sequential  integers  starting with 1. If the optional destination array d is
                               specified, then first duplicate s into d, and then sort d, leaving the indices of  the
                               source  array s unchanged. The optional string how controls the direction and the com‐
                               parison  mode.   Valid  values  for  how  are   any   of   the   strings   valid   for
                               PROCINFO["sorted_in"].   It can also be the name of a user-defined comparison function
                               as described in PROCINFO["sorted_in"].

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

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

       gsub(r, s [, t])        For each substring matching the regular expression r in the string t,  substitute  the
                               string s, and return the number of 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 discussion of the rules for &'s and backslashes in the  replacement  text
                               of sub(), gsub(), and gensub().)

       index(s, t)             Return  the  index  of  the string t in the string s, or 0 if t is not present.  (This
                               implies that character indices start at one.)

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

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

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

                               assumes that str is an octal number.  If str begins with a  leading  0x  or  0X,  str‐
                               tonum() assumes that str is a hexadecimal number.  Otherwise, decimal is assumed.

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

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

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

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

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

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

       mktime(datespec)
                 Turn datespec into a time stamp of the same form as returned by systime(), and  return  the  result.
                 The  datespec is a string of the form YYYY MM DD HH MM SS[ DST].  The contents of the string are six
                 or seven numbers representing 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, the
                 second from 0 to 60, and an optional daylight saving flag.  The values of these numbers need not  be
                 within  the  ranges specified; for example, an hour of -1 means 1 hour before midnight.  The origin-
                 zero Gregorian calendar is assumed, with year 0 preceding year 1 and year -1 preceding year 0.   The
                 time  is  assumed to be in the local timezone.  If the daylight saving flag is positive, the time is
                 assumed to be daylight saving time; if zero, the time is assumed to be standard time; and  if  nega‐
                 tive (the default), mktime() attempts to determine whether daylight saving time is in effect for the
                 specified time.  If datespec does not contain enough elements or if the resulting  time  is  out  of
                 range, mktime() returns -1.

       strftime([format [, timestamp[, utc-flag]]])
                 Format  timestamp  according to the specification in format.  If utc-flag is present and is non-zero
                 or non-null, the result is in UTC, otherwise the result is in local time.  The timestamp  should  be
                 of  the  same  form  as  returned by 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.   The
                 default format is available in PROCINFO["strftime"].  See the specification for the strftime() func‐
                 tion in ANSI C for the format conversions that are guaranteed to be available.

       systime() Return the current time of day as the number of seconds since the Epoch (1970-01-01 00:00:00 UTC  on
                 POSIX systems).

   Bit Manipulations Functions
       Gawk  supplies  the  following  bit manipulation functions.  They work by converting double-precision floating
       point values to uintmax_t integers, doing the operation, and then  converting  the  result  back  to  floating
       point.  The functions are:

       and(v1, v2)         Return the bitwise AND of the values provided by v1 and v2.
       The following function is for use with multidimensional arrays.

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

   Internationalization Functions
       The  following  functions  may  be used from within your AWK program for translating strings at run-time.  For
       full details, see GAWK: Effective AWK Programming.

       bindtextdomain(directory [, domain])
              Specify the directory where gawk looks for the .mo files, in case they will not or cannot be placed  in
              the ``standard'' locations (e.g., during testing).  It returns the directory where domain is ``bound.''
              The  default domain is the value of TEXTDOMAIN.  If directory is the null string (""), then bindtextdo‐
              main() returns the current binding for the given domain.

       dcgettext(string [, domain [, category]])
              Return the translation of string in text domain domain for locale category category.  The default value
              for domain is the current value of TEXTDOMAIN.  The default value for category is "LC_MESSAGES".
              If  you  supply  a  value for category, it must be a string equal to one of the known locale categories
              described in GAWK: Effective AWK Programming.  You must also supply a text domain.  Use  TEXTDOMAIN  if
              you want to use the current domain.

       dcngettext(string1 , string2 , number [, domain [, category]])
              Return  the plural form used for number of the translation of string1 and string2 in text domain domain
              for locale category category.  The default value for domain is the current value  of  TEXTDOMAIN.   The
              default value for category is "LC_MESSAGES".
              If  you  supply  a  value for category, it must be a string equal to one of the known locale categories
              described in GAWK: Effective AWK Programming.  You must also supply a text domain.  Use  TEXTDOMAIN  if
              you want to use the current domain.

USER-DEFINED FUNCTIONS
       Functions in AWK are defined as follows:

              function name(parameter list) { statements }

       Functions  are  executed  when  they are called from within expressions in either patterns or actions.  Actual
       parameters supplied in the function call are used to instantiate the formal parameters declared in  the  func‐
       tion.  Arrays are passed by reference, other variables are passed by value.

       Since  functions  were  not  originally  part of the AWK language, the provision for local variables is rather
       clumsy: They are declared as extra parameters in the parameter list.  The  convention  is  to  separate  local
       variables from real parameters by extra spaces in the parameter list.  For example:

              function  f(p, q,     a, b)   # a and b are local
              {
                   ...
              }

              /abc/     { ... ; f(1, 2) ; ... }

       The  left  parenthesis  in  a  function  call is required to immediately follow the function name, without any
       intervening whitespace.  This avoids a syntactic ambiguity with the concatenation operator.  This  restriction
       does not apply to the built-in functions listed above.


                   ...
              }

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

       If  --lint  has  been provided, gawk warns about calls to undefined functions at parse time, instead of at run
       time.  Calling an undefined function at run time is a fatal error.

       The word func may be used in place of function.

DYNAMICALLY LOADING NEW FUNCTIONS
       You can dynamically add new built-in functions to the running gawk interpreter.  The full details  are  beyond
       the scope of this manual page; see GAWK: Effective AWK Programming for the details.

       extension(object, function)
               Dynamically  link  the shared object file named by object, and invoke function in that object, to per‐
               form initialization.  These should both be provided as strings.  Return the value  returned  by  func‐
               tion.

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

SIGNALS
       pgawk accepts two signals.  SIGUSR1 causes it to dump a profile and function call stack to the  profile  file,
       which  is either awkprof.out, or whatever file was named with the --profile option.  It then continues to run.
       SIGHUP causes pgawk to dump the profile and function call stack and then exit.

INTERNATIONALIZATION
       String constants are sequences of characters enclosed in double quotes.  In non-English speaking environments,
       it is possible to mark strings in the AWK program as requiring translation to the local natural language. Such
       strings are marked in the AWK program with a leading underscore (“_”).  For example,

              gawk 'BEGIN { print "hello, world" }'

       always prints hello, world.  But,

              gawk 'BEGIN { print _"hello, world" }'

       might print bonjour, monde in France.

       There are several steps involved in producing and running a localizable AWK program.

       1.  Add a BEGIN action to assign a value to the TEXTDOMAIN variable to set the text domain to a  name  associ‐
           ated 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.

       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.  However, in earlier implementations, when such an assign‐
       ment 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 assign‐
       ing variables before program execution was added to accommodate applications that depended upon the old behav‐
       ior.  (This feature was agreed upon by both the Bell Laboratories and the GNU developers.)

       When processing arguments, gawk uses the special option “--” to signal the end of arguments.  In compatibility
       mode, it warns about but 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).

HISTORICAL FEATURES
       There is one feature of historical AWK implementations that gawk supports: It is possible to call the length()
       built-in function not only with no argument, but even without parentheses!  Thus,

              a = length     # Holy Algol 60, Batman!

       is the same as either of

              a = length()
              a = length($0)

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

GNU EXTENSIONS
       Gawk has a number of extensions to POSIX awk.  They  are  described  in  this  section.   All  the  extensions
       described here can be disabled by invoking gawk with the --traditional or --posix options.

       The following features of gawk are not available in POSIX awk.

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

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

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

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

       · Octal and hexadecimal constants in AWK programs.

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

       · The |& operator for creating co-processes.

       · The BEGINFILE and ENDFILE special patterns are not available.

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

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

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

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

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

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

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

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

       · The  and(),  asort(),  asorti(),  bindtextdomain(),  compl(), dcgettext(), dcngettext(), gensub(), lshift(),
         mktime(), or(), patsplit(), rshift(), strftime(), strtonum(), systime() and xor() functions.

       · Localizable strings.

       · Adding new built-in functions dynamically with the extension() 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 redirection.

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

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

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

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

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

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 compatible  with  the  new  version  of  UNIX  awk.
       Arnold Robbins is the current maintainer.

       The  initial  DOS port was done by Conrad Kwok and Scott Garfinkle.  Scott Deifik maintains the port to MS-DOS
       using DJGPP.  Eli Zaretskii maintains the port to MS-Windows using MinGW.  Pat Rankin did the port to VMS, and
       Michal  Jaegermann  did the port to the Atari ST.  The port to OS/2 was done by Kai Uwe Rommel, with contribu‐
       tions and help from Darrel Hankerson.  Andreas Buening now maintains the OS/2 port.  The late Fred  Fish  sup‐
       plied  support  for  the Amiga, and Martin Brown provided the BeOS port.  Stephen Davies provided the original
       Tandem port, and Matthew Woehlke provided changes for Tandem's POSIX-compliant systems.  Dave  Pitts  provided
       the port to z/OS.

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

BUG REPORTS
       If you find a bug in gawk, please send electronic mail to [email protected]   Please  include  your  operating
       system  and  its revision, the version of gawk (from gawk --version), which C compiler you used to compile it,
       and a test program and data that are as small as possible for reproducing the problem.

       Before sending a bug report, please do the following things.  First, verify that you have the  latest  version
       of  gawk.  Many bugs (usually subtle ones) are fixed at each release, and if yours is out of date, the problem
       may already have been solved.  Second, please see if setting  the  environment  variable  LC_ALL  to  LC_ALL=C
       causes  things  to  behave  as  you  expect.  If  so, it's a locale issue, and may or may not really be a bug.
       Finally, please read this man page and the reference manual carefully to be sure that what you think is a  bug
       really is, instead of just a quirk in the language.

       Whatever  you do, do NOT post a bug report in comp.lang.awk.  While the gawk developers occasionally read this
       newsgroup, posting bug reports there is an unreliable way to report bugs.  Instead, please use the  electronic
       mail addresses given above.

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

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

       Syntactically invalid single character programs tend to overflow the parse stack, generating a rather  unhelp‐
       ful  message.   Such  programs  are surprisingly difficult to diagnose in the completely general case, and the
       effort to do so really is not worth it.

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

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

                 { nlines++ }
            END  { print nlines }

       Precede each line by its number in the file:

            { print FNR, $0 }

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

            { print NR, $0 }

       Run an external command for particular lines of data:

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

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

COPYING PERMISSIONS
       Copyright  ©  1989,  1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2003, 2004, 2005, 2007,
       2009, 2010, 2011 Free Software Foundation, Inc.

       Permission is granted to make and distribute verbatim copies of this manual page provided the copyright notice
       and this permission notice are preserved on all copies.

       Permission  is  granted  to copy and distribute modified versions of this manual page under the conditions for
       verbatim copying, provided that the entire resulting derived work is distributed under the terms of a  permis‐
       sion notice identical to this one.

       Permission is granted to copy and distribute translations of this manual page into another language, under the
       above conditions for modified versions, except that this permission notice may  be  stated  in  a  translation
       approved by the Foundation.



Free Software Foundation                             Dec 07 2012                                              GAWK(1)