First you have to get into the particlar directory. For that run the following command:
cd /home/username/public_html
Now in order to find a specific keyword in whole public_html of that cPanel account you just need to execute the command given below:
grep -Ril "IMAGES"
The above command instructs grep to look for the Keyword “IMAGES” in the whole public_html and display the containing line.
Check out the blog and video tutorial to learn the detailed