![]() To look for more than one pattern, simply create a text file containing a list of patterns, one each line, to look for in a file or directory and use the -f parameter to load the file containing the patterns.$ grep -f ~/groups.txt /etc/group So the fourth grep command lists all of the occurrences of “unix” in all of the files in /etc and its subdirectories, where any errors are simply ignored. The next parameter, ‘-s’, tells grep to avoid reporting any errors, such as “Permission Denied” errors, to the output, so as not to pollute the output with errors. The directory, in this case, is the current one (/etc), denoted by the ‘.’. The first parameter, ‘-r’, tells grep to search through a directory recursively. Because the group file did not have “unix” as a whole word, there was no output. The third command is slightly different with the ‘-w’ parameter, which tells grep to match a whole word rather than a simple piece of text. The second command did the same, but with the -n parameter, it shows which line the pattern was found in a file. ![]() It returns all occurrences of unix_allsort (username for this computer) as a result. In this screenshot, I use grep to search for the word “unix” in the /etc/group file. Look at the terminal output for these commands: /etc$ grep unix group How to eliminate lines containing certain patterns from your search, and how to run multiple grep commands using pipes for more advanced filtering. This article will show you how to use grep when searching through text files for one or more patterns. Here, the patterns used will be simple text rather than regular expressions. ![]() The most common usage is for quickly searching a file for occurrences of a pattern, which can be in plain text, or in the form of a regular expression. This simply looks for a specified text, or pattern, in a file or an entire directory. Linux and UNIX systems come with a shell command known as ‘grep’. ![]()
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