grep cheat sheet – The Wandering Nerd

Basics
grep [pattern] FILE
grep ‘^[A,E].*o’ f.txt	Find a string starting with A or E and ending in o
grep -f pat.txt f.txt	Scan f.txt, using contents of pat.txt as regex
grep -i Gnu f.txt	Find “gnu” in f.txt, ignoring capitalization
grep -v gnu f.txt	Find all lines not containing “gnu” (invert match)
grep -w ‘a.*o’ f.txt	Find whole word matches only, ignoring substrings
grep -x ‘a.*o’ f.txt	Find whole line matches only, as in ^(a.*o)$
Output
-c	Print only the number of lines containing a match
–colo[u]r	Display matches in color
-l	Print the names of files with matches
-L	Print the names of files searched that contained no matches
-o	Print only the matched part of a line
-s	Suppress errors (such as non-existent or unreadable files)
-A n	Print n number of lines after a matching line
-B n	Print n number of lines before a matching line
-C n	Print n number of lines before and after a matching line
Output prefixes
-b	Print the byte offset of the match within the input file
-H	Print the filename containing a match
-h	Do not print the filename containing a match
-n	Print the line number of each match
-T	Print an initial Tab before matches so that output is neatly aligned
File and directory selection
-a	Process a binary file as if it were text
-D <skip\|read>	Skip or read a FIFO, device, or socket
-d <skip\|read\|recurse>	Skip, read, or recurse through a directory
–exclude ‘*.sh’	Do not search any file with the .sh suffix
–exclude-from FILE	Skip any file listed in FILE
–exclude-dir *foo	Skip any directory ending in foo
-r	When a directory is encountered, search files in it
-R	Search directories and follow symlinks
Variants
-G	Use basic regex (this is the default)
-E	Extended regex
-F	Interpret the search pattern as a fixed string, not regex
-P	Use Perl regex (PCRE)
Regular expression
.	Any single character
?	Match preceding item zero or one time
*	Match preceding item zero or more times
+	Match preceding item one or more times
{2}	Match preceding item two times
{3,}	Match preceding item three or more times
{,4}	Match preceding item at most four times
{1,5}	Match preceding item at least once, but no more than five times
[A,B]	Match A or B
[3-9]	Match all digits 3 to 9
^	Start of a line
$	End of a line
\s	Space
[:alnum:]	Alphanumeric character
[:alpha:]	Alphabetic character
[:digit:]	Digits 0 through 9
[:punct:]	Punctuation
[:space:]	Space