Determine whether a bash script was launched by icon click or from terminal

I have a script that I want to have a different behaviour depending on whether it was launched from the terminal or by (double) clicking the icon in the file manager. Can I do this?

Answer

You can use differences in the return status from tty to help you.

if tty -s;
then
    # running in a terminal
    ...
fi

(tty -s runs the tty command silently)

Exit status:

• 0 if standard input is a terminal


• 1 if standard input is not a terminal


• 2 if given incorrect arguments


• 3 if a write error occurs

Or you could use the shell's built-in tests to check whether standard input/output are from/to a terminal:

if [ -t 0 ];  # stdin
then
    # running in a terminal
    ...
fi