The VideoLAN Forums

Is it possible to use vlc cli "interactively" ?
e.g. : command one: open video file and play it; command two (while the video is playing) show subtitle menu; command 3: use subtitle X

Yes, I think you need to look into telnet interface or the rc (remote control) interface.
RC Tutorial: https://n0tablog.wordpress.com/2009/02/ ... ogramming/
VLC Wiki: https://wiki.videolan.org/Console/

Probably the remote control interface is the way to go.