Grep and regular expressions: ^, $, ., *, [ ], -i, -v, -r, -E

grep prints the lines of its input that match a pattern. On the RHCSA you use it constantly: to find a setting in a configuration file, to pick lines out of a log, or to satisfy a task such as 'save every line of /usr/share/dict/words containing the string ich into /root/lines'. The pattern is a regular expression (regex), a small language for describing text.