Linux in a Nutshell, Fourth Edition

Name

:

Synopsis

:

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

To check whether someone is logged in:

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