Awk
awk(1) is a scripting language designed for text processing.
There are several implementations:
Brian Kernighan open-sourced the original Unix implementation
GNU awk (or gawk) is an extended implementation
BusyBox implements POSIX awk(1)
the modern revivalist GoAWK
See the GNU awk User Manual for further documentation.
Example
awk 'BEGIN { print "hello world" }'
A more realistic example is extracting hostnames from the hosts file.
awk '/^[^#]/ { print $2 }' /etc/hosts
Execute a script as:
awk -f my-hosts-parser.awk /etc/hosts
Shebang
To make an awk(1) script executable, use #! /bin/awk -f as the shebang line.