Grep stdin just by typing the substring directly into the prompt.
cat users.csv | TommyThis will return all lines that contain Tommy.
A case insensitive grep is performed when all characters are lowercase.
cat users.csv | tommyThis prints all lines containing tommy, Tommy, tOmmy, toMMy, etc. Case
insensitive.
Simply make sure that the contents of the script are sourced into your bash repl.