grep program is one of the most commonly used text processing programs in Linux. It is used to search for a substring or a string pattern in files.
Let us see how to use grep and what options are available.
Consider the contents of a text file:
cat test.txt A quick brown dog jumped over the lazy fox. Linux Operating System.
To search for string
fox in this file, use:
grep fox test.txt
To invert the matching algorithm, i.e., to print non matching lines, use
grep -v fox test.txt
To search for a pattern, use the
grep -e "f.x" test.txt
To search without case sensitivity of the substring, use:
grep -i Fox test.txt
Finally, a very useful flag for grep command is
-r. It recursively scans all files and directories till the last leaf in a directory structure.
I have copied the same file used above multiple times in a directory structure for providing an example.
To search recursively in all files and directories, use:
grep -r fox grep_test/
We hope you find the information on this page helpful. If you have any questions, get in touch with us on Twitter.