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Category:AWK: Difference between revisions
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AWK is a small but powerful programming language that can process and convert text files. AWK is part of every [[Unix]]-derived system.
Each AWK program consists of pattern-action statements.
The program reads each input line, checks lines against patterns, and runs matching actions.
For programs that never read input lines, the entire program can be one <code>BEGIN { ... }</code> block.
* ''List users who have /bin/ksh as a shell.''<lang awk>$ awk -F: '$7 == "/bin/ksh" { print $1 }' /etc/passwd</lang>
AWK has only three types of variables: they are strings, floating-point numbers, and associative arrays (where every array index is a string).
Conversion between strings and numbers is automatic. AWK also has regular expressions, which appear in many AWK programs.
There are a few built-in functions, like cos() and sprintf().
* ''Find average line length.''<lang awk>$ awk '{ cnt += length($0) } END { print cnt / NR }' /etc/rc</lang>
The name "AWK" comes from the initials of Alfred Aho, Peter Weinberger and Brian Kernighan: they invented AWK during the 1970s.
A few decades later, Kernighan continues to maintain the [[nawk|reference implementation]] of AWK.
==Links==
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