Grep Cheat Sheet

Name: Grep cheat sheet
Rating: 88 (20 reviews)

This cheat sheet is intended to be a quick reminder for the main concepts involved in using the command line p

Grep regular expressions

-	-
`[A-ZÂa-z]`	Any lower and upper case letter.
`[0-9]`	Any number.
`[0-9ÂA-ZÂa-z]`	Any lower and upper case letter or digit.

-	-
`[:alpha:]`	Any lower and upper case letter.
`[:digit:]`	Any number.
`[:alnum:]`	Any lower and upper case letter or digit.
`[:space:]`	Any whitesÂpace.

-	-
`{n}`	Previous item appears exactly n times.
`{n,}`	Previous item appears n times or more.
`{,m}`	Previous item appears n times maximum.
`{n,m}`	Previous item appears between n and m times.

-	-
.	Any character.
`?`	Optional and can only occur once.
`*`	Optional and can occur more than once.
`+`	Required and can occur more than once.

Regex syntax (quickref.me)
Regex examples (quickref.me) Please refer to the full version of the regex cheat sheet for more complex requirements.

Option	Example	Operation
`-i`	grep -i ^DA demo.txt	Forgets about case sensitivity
`-w`	grep -w "of" demo.txt	Search only for the full word
`-A`	grep -A 3 'Exception' error.log	Display 3 lines after matching string
`-B`	grep -B 4 'Exception' error.log	Display 4 lines before matching string
`-C`	grep -C 5 'Exception' error.log	Display 5 lines around matching string
`-r`	grep -r 'quickref.me' /var/log/nginx/	Recursive search (within subdirs)
`-v`	grep -v 'warning' /var/log/syslog	Return all lines which don't match the pattern
`-e`	grep -e '^al' filename	Use regex (lines starting with 'al')
`-E`	grep -E 'ja(s	cks)on' filename
`-c`	grep -c 'error' /var/log/syslog	Count the number of matches
`-l`	grep -l 'robot' /var/log/*	Print the name of the file(s) of matches
`-o`	grep -o search_string filename	Only show the matching part of the string
`-n`	grep -n "go" demo.txt	Show the line numbers of the matches

Search standard output (i.e. a stream of text)

$ grep [options] search\_string

Search for an exact string in file:

$ grep [options] search\_string path/to/file

Print lines in myfile.txt containing the string "mellon"

$ grep 'mellon' myfile.txt

Wildcards are accepted in filename.