isatty -- Test for Terminal File


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 OpenEdition
terminal. isatty
returns 0 for the DDname SYSTERM when called under MVS
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