suse man page for isatty

ISATTY(3)						     Linux Programmer's Manual							 ISATTY(3)

NAME
       isatty - test whether a file descriptor refers to a terminal

SYNOPSIS
       #include <unistd.h>

       int isatty(int fd);

DESCRIPTION
       The isatty() function tests whether fd is an open file descriptor referring to a terminal.

RETURN VALUE
       isatty()  returns  1  if  fd  is an open file descriptor referring to a terminal; otherwise 0 is returned, and errno is set to indicate the
       error.

ERRORS
       EBADF  fd is not a valid file descriptor.

       EINVAL fd refers to a file other than a terminal.  POSIX.1-2001 specifies the error ENOTTY for this case.

CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001.

SEE ALSO
       fstat(2), ttyname(3)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-12-03								 ISATTY(3)