What are the default stdin and stdout for a program started from desktop on Linux?

Question

When I start a program from desktop (Ubuntu 16.04) instead of from shell so that the program is not associated with a terminal, what are the stdin and stdout for this program? Are STDIN_FILENO and STDOUT_FILENO valid file descriptors when the program starts? Where does printf write to in this case?

Answer 1

You can use the strace program to see all system calls a program is executing (like open, read, write, close). When you attatch it to the "Desktop program" (the one running your program; use pstree or proctree ), you can see what happens to file descriptors 0, 1 and 2.

See https://superuser.com/questions/606985/any-way-to-view-stdout-of-a-program-after-it-has-been-started-in-gnome-shell

Or google for "gnome run program stdout"