Stop launching a binary from command line

Question

How to make an application to prevent itself from launching from the command line?

I have a binary which should be launched by a daemon; but when somebody tries to launch the binary from command line, I should error out stating "cannot be launched from command line". Tried googling but in vain.

PS. http://www.daniweb.com/software-development/c/threads/449682/stop-launching-from-command-line I wanted to check if there are better ways than those mentioned in the link..

Answer 1

I am not sure there is a bullet proof answer (to how to prevent a program to be started from command line). You could consider

• testing with isatty(3) that STDIN_FILENO (i.e. 0) is not a tty
• try to open /dev/tty (it should fail) see tty(4)
• testing with getsid(2) that your are not in the same session than your parent, or starting a new session with setsid(2)
• calling yourself daemon(3)

And I am not sure that you always want to reject being started from a terminal. For debugging, you surely want to be able to be started from a terminal. I actually would just warn, not quit, if started from a terminal.

And you probably want to install your program outside of standard paths, maybe in some libexec/ or sbin/ directory.

See also capabilities(7), pty(7), termios(3)