!

!  -  execute a shell command

Usage:  !
   or:  !command

The ! command by itself is the same as PUSH.  It starts up a new shell
  under the MM process's shell.  When you leave the PUSHed shell (done
  by using the "exit" shell command), you will be back in MM.  PUSH is
  an advanced command for people familiar with the use of shells.

You can also use the ! mark as a prefix to an individual shell command.  
  This is the more common use of !.  It is the easiest way to issue a
  single shell command while in MM.

Example:
    Read>!ls	#The shell command "ls" shows what files you have

For more help type "help" and one of these topics
  other   push