etc/nginx/sites-available/: server_name /etc/nginx/sites-enabled/: server_name Show Only the Filename # That line is not printed when grep is invoked with -r because files inside the Nginx’s sites-enabled directory are symlinks to configuration files inside the sites-available directory.

Notice the last line of the output below. etc/nginx/sites-available/: server_name If you use the -R option, grep will follow all symbolic links: grep -R /etc The output will include matching lines prefixed by the full path to the file: /etc/hosts:127.0.0.1 Here is an example showing how to search for the string in all files inside the /etc directory: grep -r /etc Instead of -r, use the -R option (or -dereference-recursive). This allows you to easily search through your entire directory structure to find exactly what you’re looking for.

When this option is used, grep will search through all files in the specified directory, including its subdirectories, skipping the symlinks that are encountered recursively. To recursively search for a pattern, invoke grep with the -r option (or -recursive). If you wish to exclude that line from the output, you can pass it to another grep instance, as demonstrated below: ps -ef | grep www-data | grep -v grep www-data 18247 12675 4 16:00 ? 00:00:00 php-fpm: pool www As you can see in the output above, there is also a line containing the grep process. You can also chain multiple pipes in on command. This can make it much easier to find specific information within a large output.įor instance, to find out which processes are running on your system as user www-data you can use the following psĬommand: ps -ef | grep www-data www-data 18247 12675 4 16:00 ? 00:00:00 php-fpm: pool www

Using Grep to Filter the Output of a Command #Ī command’s output can be filtered with grep through piping, and only the lines matching a given pattern will be printed on the terminal.

Use the -v ( or -invert-match) option to display the lines that do not match a pattern.įor example, to print the lines that do not contain the string “nologin” you would use: grep -v nologin /etc/passwd root:x:0:0:root:/root:/bin/bashĬolord:x:124:124::/var/lib/colord:/bin/false If the string contains spaces, you need to enclose it in single or double quotation marks: grep 'Gnome Display Manager' /etc/passwd Invert Match (Exclude) # The output will look something like this: root:x:0:0:root:/root:/bin/bash The most basic usage of the grep command is to search for a string (text) in a file.įor instance, to find all the lines containing the string “bash” in the /etc/passwdįile, you would run the following command: grep bash /etc/passwd To be able to search the file, the user running the command must have read access to the file. The items in square brackets are optional.

Command line find file regex