@node isatty, unix
@subheading Syntax

@example
#include <unistd.h>

int isatty(int fd);
@end example

@subheading Description

Tells if the file descriptor refers to a terminal device or not.

@subheading Return Value

Nonzero if @var{fd} is a terminal device, zero  otherwise.

@subheading Portability

@portability !ansi, posix

@subheading Example

@example
if (isatty(1))
  fflush(stdout);
@end example