awk

AWK is a domain-specific language and command-line utility designed for text processing and data extraction. It was developed for Unix by Alfred Aho, Peter Weinberger, and Brian Kernighan and is named after their initials. Over time, several implementations have appeared, including the original awk, nawk, mawk, and GNU awk (gawk), with gawk becoming a widely used standard in many environments.

An awk program consists of pattern-action statements. It processes input as a sequence of records, with the record separator RS (default newline). Each record is split into fields by the field separator FS (default whitespace). The fields are referenced as $1, $2, ..., and the entire record as $0. Built-in variables NR (current record number) and NF (number of fields) are commonly used, as are OFS and OFMT for output formatting. The language supports control structures, expressions, arrays (often associative), and user-defined functions.

The typical form is pattern { action }. If the pattern matches, the action is executed; if the pattern is omitted, the action runs for every record. If the action is omitted, awk prints the current record. awk provides print and printf for output, along with a range of string and math functions such as length, substr, split, match, and index. External commands can be invoked via system or by piping output.

Common uses include filtering, reformatting, field-based reports, and simple data analysis in pipelines. Example: awk '{print $1, $NF}' file prints the first and last field; awk '/pattern/ {print $0}' file selects lines matching a pattern.

Awk is widely available on Unix-like systems; GNU awk (gawk) is common on Linux, while mawk is used in some distributions. It remains a versatile tool for quick text-oriented data processing.