(gawk.info)POSIX/GNU

Extensions in `gawk' Not in POSIX `awk'
=======================================

   The GNU implementation, `gawk', adds a number of features.  This
sections lists them in the order they were added to `gawk'.  They can
all be disabled with either the `--traditional' or `--posix' options
(Note: Command Line Options.).

   Version 2.10 of `gawk' introduced these features:

   * The `AWKPATH' environment variable for specifying a path search for
     the `-f' command line option (*note Command Line Options:
     Options.).

   * The `IGNORECASE' variable and its effects (Note: Case-sensitivity
     in Matching.).

   * The `/dev/stdin', `/dev/stdout', `/dev/stderr', and `/dev/fd/N'
     file name interpretation (*note Special File Names in `gawk':
     Special Files.).

   Version 2.13 of `gawk' introduced these features:

   * The `FIELDWIDTHS' variable and its effects (Note: Reading
     Fixed-width Data.).

   * The `systime' and `strftime' built-in functions for obtaining and
     printing time stamps (Note: Functions for Dealing with Time
     Stamps.).

   * The `-W lint' option to provide source code and run time error and
     portability checking (Note: Command Line Options.).

   * The `-W compat' option to turn off these extensions (Note: Command
     Line Options.).

   * The `-W posix' option for full POSIX compliance (Note: Command
     Line Options.).

   Version 2.14 of `gawk' introduced these features:

   * The `next file' statement for skipping to the next data file
     (Note: The `nextfile' Statement.).

   Version 2.15 of `gawk' introduced these features:

   * The `ARGIND' variable, that tracks the movement of `FILENAME'
     through `ARGV'  (Note: Built-in Variables.).

   * The `ERRNO' variable, that contains the system error message when
     `getline' returns -1, or when `close' fails (Note: Built-in
     Variables.).

   * The ability to use GNU-style long named options that start with
     `--' (Note: Command Line Options.).

   * The `--source' option for mixing command line and library file
     source code (Note: Command Line Options.).

   * The `/dev/pid', `/dev/ppid', `/dev/pgrpid', and `/dev/user' file
     name interpretation (Note: Special File Names in `gawk'.
).

   Version 3.0 of `gawk' introduced these features:

   * The `next file' statement became `nextfile' (Note: The `nextfile'
     Statement.).

   * The `--lint-old' option to 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.).

   * The `--traditional' option was added as a better name for
     `--compat' (Note: Command Line Options.).

   * The ability for `FS' to be a null string, and for the third
     argument to `split' to be the null string (Note: Making Each
     Character a Separate Field.).

   * The ability for `RS' to be a regexp (Note: How Input is Split into
     Records.).

   * The `RT' variable (*note How Input is Split into Records:
     Records.).

   * The `gensub' function for more powerful text manipulation (Note:
     Built-in Functions for String Manipulation.).

   * The `strftime' function acquired a default time format, allowing
     it to be called with no arguments (Note: Functions for Dealing
     with Time Stamps.).

   * Full support for both POSIX and GNU regexps (Note: Regular
     Expressions.).

   * The `--re-interval' option to provide interval expressions in
     regexps (Note: Regular Expression Operators.).

   * `IGNORECASE' changed, now applying to string comparison as well as
     regexp operations (*note Case-sensitivity in Matching:
     Case-sensitivity.).

   * The `-m' option and the `fflush' function from the Bell Labs
     research version of `awk' (Note: Command Line Options.;
     also Note: Built-in Functions for Input/Output.).

   * The use of GNU Autoconf to control the configuration process
     (Note: Compiling `gawk' for Unix.).

   * Amiga support (Note: Installing `gawk' on an Amiga.
).