![]() Grep will display all lines where the string is embedded in larger strings while searching for a string. "Zebra" will match "zebra", "ZEbrA", or any other upper and lower case letter combination for that string. However, if you use the -i option to perform a case-insensitive search, it will match both upper and lower case letters: grep -i Zebra /usr/share/words When searching for Zebra without any options, for example, the following command will not return any results, despite the fact that there are matching lines: grep Zebra /usr/share/words When using grep, use the -i option to ignore case when searching (or -ignore-case). The uppercase and lowercase characters are treated separately in this scenario. Usually, the -l option is combined with the recursive option -R: grep -Rl /tmp conf and prints just the names of the files that contain the string : grep -l *.conf The command below searches the current working directory for all files ending in. Use the -l (or -files-with-matches) option to suppress the default grep output and only print the names of files containing the matched pattern. etc/nginx/sites-available/: server_name /etc/nginx/sites-enabled/: server_name Show Only the Filename Because files in Nginx's sites-enabled directory are symlinks to configuration files in the sites-available directory, that line is not shown when grep is run with -r. etc/nginx/sites-available/: server_name grep will follow all symbolic links if you use the -R option: grep -R /etc You will get an output like below: Output ![]() Here's an example of how to search all files in the /etc directory for the string : grep -r /etc Instead of -r, use the -R option to follow all symbolic links (or -dereference-recursive). When this option is supplied, grep will scan all files in the specified directory, skipping any recursively encountered symlinks. Invoke grep with the -r option to recursively search for a pattern (or -recursive). ![]() Pass the output to another grep instance as described below if you don't want that line to be displayed. ![]() There is also a line in the output above that contains the grep process, as you can see. You can also use a single command to bring in several pipes. You can use the ps command to see which processes are running on your system as user www-data, for example: ps -ef | grep www-data The output of a command can be filtered using grep and pipe, with just the lines matching a specific pattern being printed on the terminal. Use Grep to Filter the Output of a Command To print the lines that do not contain the string nologin, for example, type: grep -v nologin /etc/passwdĬolord:x:124:124::/var/lib/colord:/bin/false Use the -v (or -invert-match) option to display lines that do not match a pattern. If the string contains spaces, use single or double quotation marks to surround it: grep "Gnome Display Manager" /etc/passwd This is what the output should look like: root:x:0:0:root:/root:/bin/bash The grep command's most basic use is to look for a string (text) in a file.įor example, to see all the entries in the /etc/passwd file that contains the string bash, use the following command: grep bash /etc/passwd The user performing the command must have read access to the file in order to search it. grep has a lot of settings that govern how it behaves.
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