This action type is used to run a program when a message arrives. The following
type-specific parameters are supported:
- Command line: the name of executable file and the command-line parameters for the program. Variable references are allowed, but there is something special with them: none of words in the command line may be splitted up to several parameters due to spaces appearing in the variable's value.
- Store output to variable: the name of the new variable that will contain all data that the program usually sends to the standard output (the console). A side-effect of this parameter is that if it's non-blank, the program must exit before the message is passed to another rules (and before another messages may be received). If it's blank, the program is run in the background.
