Detect pipe from running C program

jhwilliams · 01-24-2009, 07:51 PM

I'm looking for a way to detect whether or not a program has been called from pipe, e.g.

Code:

whatever | my_program

versus simply just being exectuated directly:

Code:

my_program

Why? In the first case, I want to run the program non-interactively, and in the latter case I want to print out user-friendly messages. I've been thinking along the lines of some check I haven't yet found, like:

Code:

if( stream_buffer_is_not_empty() )
    print_interactive_messages();

Any ideas?

Thanks to you!

Jameson

SciYro · 01-24-2009, 10:34 PM

Code:

#include <stdio.h>
#include <unistd.h>

int main (argc, argv)
  int argc;
  char** argv;
{
    if (isatty (STDIN_FILENO))
        printf ("Not a pipe.\n");
     else printf ("Its a pipe.\n");

     return 0;
}

The isatty function, as defined in unistd.h seems to work.