A.5 Extensions in gawk Not in POSIX awk

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

Version 2.10 of gawk introduced the following features:

• The AWKPATH environment variable for specifying a path search for the `-f' command-line option (see section Command-Line Options).

• The IGNORECASE variable and its effects (see section Case Sensitivity in Matching).

• The `/dev/stdin', `/dev/stdout', `/dev/stderr' and `/dev/fd/N' special file names (see section Special File Names in gawk).

Version 2.13 of gawk introduced the following features:

• The FIELDWIDTHS variable and its effects (see section Reading Fixed-Width Data).

• The systime and strftime built-in functions for obtaining and printing timestamps (see section Using gawk's Timestamp Functions).

• The `-W lint' option to provide error and portability checking for both the source code and at runtime (see section Command-Line Options).

• The `-W compat' option to turn off the GNU extensions (see section Command-Line Options).

• The `-W posix' option for full POSIX compliance (see section Command-Line Options).

Version 2.14 of gawk introduced the following feature:

• The next file statement for skipping to the next data file (see section Using gawk's nextfile Statement).

Version 2.15 of gawk introduced the following features:

• The ARGIND variable, which tracks the movement of FILENAME through ARGV (see section 7.5 Built-in Variables).

• The ERRNO variable, which contains the system error message when getline returns -1 or when close fails (see section 7.5 Built-in Variables).

• The `/dev/pid', `/dev/ppid', `/dev/pgrpid', and `/dev/user' file name interpretation (see section Special File Names in gawk).

• The ability to delete all of an array at once with `delete array' (see section The delete Statement).

• The ability to use GNU-style long-named options that start with `--' (see section Command-Line Options).

• The `--source' option for mixing command-line and library file source code (see section Command-Line Options).

Version 3.0 of gawk introduced the following features:

• IGNORECASE changed, now applying to string comparison as well as regexp operations (see section Case Sensitivity in Matching).

• The RT variable that contains the input text that matched RS (see section How Input Is Split into Records).

• Full support for both POSIX and GNU regexps (see section Regular Expressions).

• The gensub function for more powerful text manipulation (see section String Manipulation Functions).

• The strftime function acquired a default time format, allowing it to be called with no arguments (see section Using gawk's Timestamp Functions).

• The ability for FS and for the third argument to split to be null strings (see section Making Each Character a Separate Field).

• The ability for RS to be a regexp (see section How Input Is Split into Records).

• The next file statement became nextfile (see section Using gawk's nextfile Statement).

• The `--lint-old' option to warn about constructs that are not available in the original Version 7 Unix version of awk (see section Major Changes Between V7 and SVR3.1).

• The `-m' option and the fflush function from the Bell Laboratories research version of awk (see section Command-Line Options; also see section Input/Output Functions).

• The `--re-interval' option to provide interval expressions in regexps (see section Regular Expression Operators).

• The `--traditional' option was added as a better name for `--compat' (see section Command-Line Options).

• The use of GNU Autoconf to control the configuration process (see section Compiling gawk for Unix).

• Amiga support (see section Installing gawk on an Amiga).

Version 3.1 of gawk introduced the following features:

• The BINMODE special variable for non-POSIX systems, which allows binary I/O for input and/or output files (see section Using gawk on PC Operating Systems).

• The LINT special variable, which dynamically controls lint warnings (see section 7.5 Built-in Variables).

• The PROCINFO array for providing process-related information (see section 7.5 Built-in Variables).

• The TEXTDOMAIN special variable for setting an application's internationalization text domain (see section 7.5 Built-in Variables, and Internationalization with gawk).

• The ability to use octal and hexadecimal constants in awk program source code (see section Octal and Hexadecimal Numbers).

• The `|&' operator for two-way I/O to a coprocess (see section Two-Way Communications with Another Process).

• The `/inet' special files for TCP/IP networking using `|&' (see section Using gawk for Network Programming).

• The optional second argument to close that allows closing one end of a two-way pipe to a coprocess (see section Two-Way Communications with Another Process).

• The optional third argument to the match function for capturing text-matching subexpressions within a regexp (see section String Manipulation Functions).

• Positional specifiers in printf formats for making translations easier (see section Rearranging printf Arguments).

• The asort function for sorting arrays (see section Sorting Array Values and Indices with gawk).

• The bindtextdomain and dcgettext functions for internationalization (see section Internationalizing awk Programs).

• The extension built-in function and the ability to add new built-in functions dynamically (see section Adding New Built-in Functions to gawk).

• The mktime built-in function for creating timestamps (see section Using gawk's Timestamp Functions).

• The and, or, xor, compl, lshift, rshift, and strtonum built-in functions (see section Using gawk's Bit Manipulation Functions).

• The support for `next file' as two words was removed completely (see section Using gawk's nextfile Statement).

• The `--dump-variables' option to print a list of all global variables (see section Command-Line Options).

• The `--gen-po' command-line option and the use of a leading underscore to mark strings that should be translated (see section Extracting Marked Strings).

• The `--non-decimal-data' option to allow non-decimal input data (see section Allowing Non-Decimal Input Data).

• The `--profile' option and pgawk, the profiling version of gawk, for producing execution profiles of awk programs (see section Profiling Your awk Programs).

• The `--enable-portals' configuration option to enable special treatment of pathnames that begin with `/p' as BSD portals (see section Using gawk with BSD Portals).

• The use of GNU Automake to help in standardizing the configuration process (see section Compiling gawk for Unix).

• The use of GNU gettext for gawk's own message output (see section gawk Can Speak Your Language).

• BeOS support (see section Installing gawk on BeOS).

• Tandem support (see section Installing gawk on a Tandem).

• The Atari port became officially unsupported (see section Installing gawk on the Atari ST).

• The source code now uses new-style function definitions, with ansi2knr to convert the code on systems with old compilers.