Question

My program reads a list of integers from user input [ keyboard] and calculates some statistics

The user enters ‘x’ to terminate the input process.

So for example,

Enter integers separated by space ( enter x to quit) : 1 2 3 4 5 x

But now I want to include the inputs to be read from file redirection also. So if the numbers followed by x is in a data file, the program should take it from there if not then prompt the user

Answer 1

use isatty for your file descriptor
(0 for standard input)

example:

#include <unistd.h>
main(){
  if(isatty(0))
    puts("tty");  // print some prompt
  else
    puts("pipe"); // not really needed in your case
}