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GNU grep Command Guide

This document provides a cheat sheet for using the GNU grep command to find patterns in text files and streams. It lists basic usage such as searching for a pattern in a file, options for ignoring case or inverting matches, and output options. It also covers regular expressions, file selection criteria, and variants for different regex types.

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Vinay K
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362 views2 pages

GNU grep Command Guide

This document provides a cheat sheet for using the GNU grep command to find patterns in text files and streams. It lists basic usage such as searching for a pattern in a file, options for ignoring case or inverting matches, and output options. It also covers regular expressions, file selection criteria, and variants for different regex types.

Uploaded by

Vinay K
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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GNU grep Cheat Sheet

GNU grep finds patterns in text files and streams.

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

Seth Kenlon CC BY-SA 4.0 Opensource.com


GNU grep Cheat Sheet

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 [:alnum:] Alphanumeric character
[3-9] Match all digits 3 to 9 [:alpha:] Alphabetic character
^ Start of a line [:digit:] Digits 0 through 9
$ End of a line [:punct:] Punctuation
\s Space [:space:] Space

Seth Kenlon CC BY-SA 4.0 Opensource.com

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