isatty

isatty

Test for Terminal File

Portability: POSIX.1 conforming, UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
EXAMPLE
RELATED FUNCTIONS
SEE ALSO

SYNOPSIS

#include <lcio.h>

int isatty(int fn);

The syntax for the POSIX implementation is

#include <sys/types.h>
#include <unistd.h>

int isatty(int fn);

DESCRIPTION

isatty tests whether the file associated with file number fn is an interactive terminal. isatty returns a non-zero value if the file number represents a TSO terminal, a CMS terminal, or an USS terminal. isatty returns 0 for the DDname SYSTERM when called under OS/390 batch.

RETURN VALUE

A nonzero value is returned if the file number is associated with an interactive terminal; otherwise, 0 is returned.

EXAMPLE

#include <lcio.h>
#include <stdio.h>

double point[40];

main()
{
   FILE *f;
   int index = 0;
   double sum = 0.0;
   double avg ;
   int nopoints;
   int fn =0;

      /* If stdin is the terminal, (fileno(stdin) is always 0). */
   if (isatty(fn))

      /* Tell user to enter data points - max. = 39.            */
   puts("Enter data points (-1 to indicate end of list).");

   for(;;){
         /* Read number; check for end of file.                 */
      if (scanf("%le", &point[index]) <= 0)
         break;
      if (point[index] == -1) break;
      sum += point[index];
      ++index;
   }

   nopoints = index;
   avg = sum / nopoints;
   printf("%d points read.\n", nopoints);
   printf("%f = average.\n", avg);
}

RELATED FUNCTIONS

fattr , fstat , fterm

SEE ALSO

I/O Functions

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