Linux in a Nutshell, Third Edition

Name

:

Synopsis

:

Description

Null command. Returns an exit status of 0. Sometimes used as the first character in a file to denote a bash script. Shell variables can be placed after the : to expand them to their values.

Example

Check whether someone is logged in:

                     if who | grep $1 > /dev/null
                     then :     # do nothing
                          # if pattern is found
                     else echo "User $1 is not logged in"
                     fi