Grep

grep is a command that reads strings and only outputs them if they match a pattern. For example to show all lines in a file syslog that contain the string Nov call it like:

grep "Nov" syslog

Examples

• Show all lines that do not contain blabla

grep -v blabla filename.txt

• Match any character

With a dot (.) you can match any character

grep -E "L.nux"

Matches Linux, Lanux L nux, but not Lnux

• Match all characters

With a .* you can match an arbitrary count of any character

grep -E "L.*nux"

Matches Linux, Liinux, Lanux, L nux and Lnux

• Match any character but blank

grep -E "L[^ ]nux"

Matches Linux, Lanux, but not Lnux and not L nux

• Match any line starting with a character

grep -E "U"

Matches all lines starting with U

• Show all files containing content

grep -ir "content" *

Usecases

Show all running processes

ps auxf | grep -E "^[^ ]+ +[^ ]+ +[^ ]+ +[^ ]+ +[^ ]+ +[^ ]+ +[^ ]+ +R"

See also

• regex