Linux tr command (translate)
The tr command is used to translate text.
Example
root@ok:~# echo "serverok" | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ SERVEROK root@ok:~#
You can also use
root@ok:~# echo "serverok" | tr "a-z" "A-Z" SERVEROK root@ok:~#
To change specific chars
root@ok:~# echo "serverok" | tr "sok" "SOK" ServerOK root@ok:~#
To delete char, use -d option
root@ok:~# echo "serverok" | tr -d "ok" server root@ok:~#
See Linux Commands