(gawk.info)Options

Command Line Options
====================

   Options begin with a dash, and consist of a single character.  GNU
style long options consist of two dashes and a keyword.  The keyword
can be abbreviated, as long the abbreviation allows the option to be
uniquely identified.  If the option takes an argument, then the keyword
is either immediately followed by an equals sign (`=') and the
argument's value, or the keyword and the argument's value are separated
by whitespace.  For brevity, the discussion below only refers to the
traditional short options; however the long and short options are
interchangeable in all contexts.

   Each long option for `gawk' has a corresponding POSIX-style option.
The options and their meanings are as follows:

`-F FS'
`--field-separator FS'
     Sets the `FS' variable to FS (Note: Specifying How Fields are
     Separated.).

`-f SOURCE-FILE'
`--file SOURCE-FILE'
     Indicates that the `awk' program is to be found in SOURCE-FILE
     instead of in the first non-option argument.

`-v VAR=VAL'
`--assign VAR=VAL'
     Sets the variable VAR to the value VAL *before* execution of the
     program begins.  Such variable values are available inside the
     `BEGIN' rule (Note: Other Command Line Arguments.
).

     The `-v' option can only set one variable, but you can use it more
     than once, setting another variable each time, like this: `awk
     -v foo=1 -v bar=2 ...'.

`-mf NNN'
`-mr NNN'
     Set various memory limits to the value NNN.  The `f' flag sets the
     maximum number of fields, and the `r' flag sets the maximum record
     size.  These two flags and the `-m' option are from the Bell Labs
     research version of Unix `awk'.  They are provided for
     compatibility, but otherwise ignored by `gawk', since `gawk' has
     no predefined limits.

`-W GAWK-OPT'
     Following the POSIX standard, options that are implementation
     specific are supplied as arguments to the `-W' option.  These
     options also have corresponding GNU style long options.  See below.

`--'
     Signals the end of the command line options.  The following
     arguments are not treated as options even if they begin with `-'.
     This interpretation of `--' follows the POSIX argument parsing
     conventions.

     This is useful if you have file names that start with `-', or in
     shell scripts, if you have file names that will be specified by
     the user which could start with `-'.

   The following `gawk'-specific options are available:

`-W traditional'
`-W compat'
`--traditional'
`--compat'
     Specifies "compatibility mode", in which the GNU extensions to the
     `awk' language are disabled, so that `gawk' behaves just like the
     Bell Labs research version of Unix `awk'.  `--traditional' is the
     preferred form of this option.  Note: Extensions in `gawk' Not in
     POSIX `awk', which summarizes the extensions.  Also see
     Note: Downward Compatibility and Debugging.

`-W copyleft'
`-W copyright'
`--copyleft'
`--copyright'
     Print the short version of the General Public License, and then
     exit.  This option may disappear in a future version of `gawk'.

`-W help'
`-W usage'
`--help'
`--usage'
     Print a "usage" message summarizing the short and long style
     options that `gawk' accepts, and then exit.

`-W lint'
`--lint'
     Warn about constructs that are dubious or non-portable to other
     `awk' implementations.  Some warnings are issued when `gawk' first
     reads your program.  Others are issued at run-time, as your
     program executes.

`-W lint-old'
`--lint-old'
     Warn about constructs that are not available in the original
     Version 7 Unix version of `awk' (Note: Major Changes between V7
     and SVR3.1.1.).

`-W posix'
`--posix'
     Operate in strict POSIX mode.  This disables all `gawk' extensions
     (just like `--traditional'), and adds the following additional
     restrictions:

        * `\x' escape sequences are not recognized (Note: Escape
          Sequences.).

        * Newlines do not act as whitespace to separate fields when
          `FS' is equal to a single space.

        * The synonym `func' for the keyword `function' is not
          recognized (Note: Function Definition Syntax.
).

        * The operators `**' and `**=' cannot be used in place of `^'
          and `^=' (Note: Arithmetic Operators., and
          also Note: Assignment Expressions.).

        * Specifying `-Ft' on the command line does not set the value
          of `FS' to be a single tab character (Note: Specifying How
          Fields are Separated.).

        * The `fflush' built-in function is not supported (Note:
          Built-in Functions for Input/Output.).

     If you supply both `--traditional' and `--posix' on the command
     line, `--posix' will take precedence. `gawk' will also issue a
     warning if both options are supplied.

`-W re-interval'
`--re-interval'
     Allow interval expressions (*note Regular Expression Operators:
     Regexp Operators.), in regexps.  Because interval expressions were
     traditionally not available in `awk', `gawk' does not provide them
     by default. This prevents old `awk' programs from breaking.

`-W source PROGRAM-TEXT'
`--source PROGRAM-TEXT'
     Program source code is taken from the PROGRAM-TEXT.  This option
     allows you to mix source code in files with source code that you
     enter on the command line. This is particularly useful when you
     have library functions that you wish to use from your command line
     programs (Note: The `AWKPATH' Environment Variable.
).

`-W version'
`--version'
     Prints version information for this particular copy of `gawk'.
     This allows you to determine if your copy of `gawk' is up to date
     with respect to whatever the Free Software Foundation is currently
     distributing.  It is also useful for bug reports (Note: Reporting
     Problems and Bugs.).

   Any other options are flagged as invalid with a warning message, but
are otherwise ignored.

   In compatibility mode, as a special case, if the value of FS supplied
to the `-F' option is `t', then `FS' is set to the tab character
(`"\t"').  This is only true for `--traditional', and not for `--posix'
(Note: Specifying How Fields are Separated.).

   The `-f' option may be used more than once on the command line.  If
it is, `awk' reads its program source from all of the named files, as
if they had been concatenated together into one big file.  This is
useful for creating libraries of `awk' functions.  Useful functions can
be written once, and then retrieved from a standard place, instead of
having to be included into each individual program.

   You can type in a program at the terminal and still use library
functions, by specifying `-f /dev/tty'.  `awk' will read a file from
the terminal to use as part of the `awk' program.  After typing your
program, type `Control-d' (the end-of-file character) to terminate it.
(You may also use `-f -' to read program source from the standard
input, but then you will not be able to also use the standard input as a
source of data.)

   Because it is clumsy using the standard `awk' mechanisms to mix
source file and command line `awk' programs, `gawk' provides the
`--source' option.  This does not require you to pre-empt the standard
input for your source code, and allows you to easily mix command line
and library source code (*note The `AWKPATH' Environment Variable:
AWKPATH Variable.).

   If no `-f' or `--source' option is specified, then `gawk' will use
the first non-option command line argument as the text of the program
source code.

   If the environment variable `POSIXLY_CORRECT' exists, then `gawk'
will behave in strict POSIX mode, exactly as if you had supplied the
`--posix' command line option.  Many GNU programs look for this
environment variable to turn on strict POSIX mode. If you supply
`--lint' on the command line, and `gawk' turns on POSIX mode because of
`POSIXLY_CORRECT', then it will print a warning message indicating that
POSIX mode is in effect.

   You would typically set this variable in your shell's startup file.
For a Bourne compatible shell (such as Bash), you would add these lines
to the `.profile' file in your home directory.

     POSIXLY_CORRECT=true
     export POSIXLY_CORRECT

   For a `csh' compatible shell,(1) you would add this line to the
`.login' file in your home directory.

     setenv POSIXLY_CORRECT true

   ---------- Footnotes ----------

   (1)  Not recommended.