How to use the grep tool
The grep tool is built into the operating system, so you don’t need to install it.
The simplest syntax to find a string in a single file using the grep command is:
grep ‘searched-word’ filename
By default, the search with grep is case sensitive.
Let’s gradually add the most useful options to our search.
1. Make the search case-insensitive with the "-i" option: grep 'searched-word' filename
2. Search recursively in all files in a given directory with the "-r" option: grep 'searched-word' '/directory'
3. Search whole words only with the "-w" option: grep 'searched-word' '/directory'
4. Print the line numbers in which the searched word was found with the "-n" option: grep 'searched-word' '/directory'
5. Search for multiple words syntax: grep 'word1|word2|word3' '/directory'
Many other useful grep options can be found in the official Grep Manual.