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. 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.įor example, 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 To display the lines that do not match a pattern, use the -v ( or -invert-match) option.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 includes spaces, you need to enclose it in single or double quotation marks: grep "Gnome Display Manager" /etc/passwd Invert Match (Exclude) # The output should 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 example, to display all the lines containing the string bash from 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.
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