Does any Linux or Mac command line tool support vocoder effect?
If by vocoder you mean "voice simulator" you can try the following cli on your Mac's terminal:
$say "Hello World"
For more informations about the command line type in
$man say
If you search for the other type of vocoder, try Jack with a normal vst plugin like Matrix on your Mac.
If you are on Linux it's even better here is what I've found searching on google : vocoder linux jack.
A simple aliasing of your script could create a simple command line for you to call in order to use the vocoder.
Best,
