gawk

gawk is the GNU implementation of the AWK programming language, a domain-specific tool for pattern scanning and text processing. Like other AWK variants, it reads input line by line, splits each line into fields, and executes actions based on pattern matches. Gawk is part of the GNU project and is distributed under the GNU General Public License.

Compared with other AWK implementations, gawk adds extensions and enhancements that remain compatible with POSIX AWK. It provides associative arrays, a broader set of built-in functions, and extensive string and data-processing facilities. It also includes advanced features such as asort and asorti for sorting associative arrays, gensub for flexible regular-expression substitution, and the ability to read and execute programs from files. In addition, gawk accepts a range of command-line options to control behavior, including -F to set the input field separator and -v to define variables, and -W posix to request strict POSIX compatibility. In newer versions, gawk supports in-place editing of files with the -i option.

Usage examples illustrate its typical role: gawk -F: '/root/ {print $1}' /etc/passwd prints usernames with a root field; gawk -v min=10 'NR > min {print NR ":" $0}' file prints lines after a given line number. gawk programs can be written inline as one-liners or saved in script files and executed with the -f option.

gawk is widely available on Linux, macOS, BSD, and other Unix-like systems and can also run on Windows through environments such as Cygwin or MSYS2. It is a free software project and its source code and binaries are distributed under the GNU General Public License, ensuring access to the source and the ability to modify and share.