locate — Searching for files from a cached database of files on the system
locate [-i] {search string}
locate [-i] -r {regular expression search string}
Note that the database is created by the updatedb command. Typically, there is a cron job in /etc/cron.daily which will run updatedb daily, but not all systems are setup to do so.
Find all filenames containing the word devel in their absolute path
locate devel
Look for .txt files and .TXT files
locate -i "*.txt"
Find all pdf files under user's home directory
locate "*.pdf" | grep /home/user
Locate all c source code files whose names only contain the letters a-f
locate -r "/[a-f]*\.c$"