Use -
to left align a field.
printf "Echoing random number %-5s [ OK ]" $RAND_NUM
Alternatively, if you’re on a Red Hat Linux system there are predefined functions that will print out green OK and red FAILED prompts (the ones you see during bootup):
#!/bin/bash
. /etc/init.d/functions
echo -n "Frobbing widget:"
frob_widget && echo_success || echo_failure
echo