Chapter Contents

Previous

Next
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


Chapter Contents

Previous

Next

Top of Page

Copyright © 2001 by SAS Institute Inc., Cary, NC, USA. All rights reserved.