grep searches the input files for lines containing a match to a given pattern list. When it finds a match in a line, it copies the lines to standard output.

How to grep sur le bout des doigts !

Search for a string in a file

This is a basic usage of grep command.

grep Lorem index.html

Here, we are looking for the word “Lorem” in index.html file.

Insensitive case search

Searching for a word with insensitive case.

grep -i "Lorem" index.html

Here, we are looking for the word Lorem written with or without upper case.

Searching for a string in multiple files.

This command will search for “Lorem” in different files.

grep Lorem index*.*

Here, we are looking for Lorem in all the files that have a name starting with “index” with all the extension available in the directory where the file is.

Searching for a string using a regular expresion pattern

This one is a very powerful feature, if you use it wisely.

grep "Lorem.*amet" index.html

Here, we are looking for every line that contain the pattern that starts with “Lorem” and ends with “dance”, whatever is in between.

Display line numbers.

Using the -n option, enable to display the line number which contains the matched pattern.

grep -n Lorem index.html

Highlighting the result

Using the –color option, enable to highlight the sucessful matches.

grep --color Lorem index.html

Search for the lines excluding a specific pattern

Using the -v option, enable to list all the lines that do not contain the pattern.

grep -v Lorem index.html

Search the pattern recursively

Using the -r option, enable to search in all the files of a directory recursively.

grep -r Lorem var/www/

Number of times a pattern matches in a file

Using the -c option, enable to count the number of times a pattern matches in a file

grep -c "Lorem ipsum" index.html

Here it is ! Now, you have everything on sur le bout des doigts (on the thumbs).