Grep Cheat Sheet
Usage
Grep standard output (i.e. a stream of tex t)
grep [-opt
๎
ions] โstringโ
Grep the content of a file
grep [-opt
๎
ions] โstringโ filename
Wildcards are accepted in filen
๎
ame.
General Regular Expression Processor
Oper๎ation Option Exam๎ple
Find a string in 1 or more files grep 'string' filename1 filename2 ... filena๎men
Case insens๎itive search i grep -i 'string' filename
Use regular expres๎sions (regex) grep 'regex' filename
Look for words w grep -w 'word' filename
Display n lines after matching string A grep -A n 'string' filename
Display n lines before matching string B grep -B n 'string' filename
Display n lines around matching string C grep -C n 'string' filename
Recu๎rsive grep r grep -r 'hacke๎rs-๎clu๎b.cn' /var/l๎๎og๎/๎a๎pa๎๎che๎๎2/๎a๎r๎ch๎๎ives/
Return all lines which don't match the pa ttern v grep -v 'warning' /var/l๎og/๎syslog
Use regex e grep -e 'string1' -e 'string2' filename
grep --regexp 'string' filename
Return lines starting with 'al' grep -e '^al' filename
Use extended regex E grep -E 'apach๎e|w๎hee๎l|root' filename
Get lines containing 1+ w grep -E 'w+' filename
Get lines with 3 w in a row (www) grep -E 'w{3}' filename
Get lines containing between 3 and 6 m in a row grep -E 'm{3,6}' filename
Get lines containing jason or jackson grep -E 'ja(s|๎cks)on' filename
Count results c grep -c 'error' /var/l๎og/๎syslog
Display filename l grep -l 'string' /var/log/*
Only show the matching part of the strin g o grep -o 'string' filename
Show line number n grep -n 'string' filename
About grep -E: In basic regular e xpres๎sions the meta-c๎har๎acters โ?โ, โ+โ, โ{โ, โ|โ, โ(โ, and โ)โ lose their special meaning; instead use the backsl๎ashed
versions โ\?โ, โ\+โ, โ\{โ, โ\|โ, โ\(โ, and โ\)โ.
GNU grep -E emulates classic meta-c๎har๎acters. The command โgrep -E '{1'โ searches for the 2-char๎acter string โ{1โ instead of reporting an error.
POSIX allows this behavior as an extension, but portable scripts should avoid it.
