Executes command. You should not use an ampersand '&' at the end of the command. You probably want to use an additional "exec" at the beginning of command. Without that, the shell that fvwm invokes to run your command stays until the command exits. In effect, you'll have twice as many processes running as you need. Note that some shells are smart enough to avoid this, but it never hurts to include the "exec" anyway.

The following example binds function key F1 in the root window, with no modifiers, to the exec function. The program rxvt is started with an assortment of options.

Key F1 R N Exec exec rxvt -fg yellow -bg blue \
  -e /bin/tcsh

Note that this function doesn't wait for command to complete, so things like:

Exec "echo AddToMenu ... > /tmp/file"
Read /tmp/file

do not work reliably (see the PipeRead command).