isatty(3)

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

LIBRARY
Standard C library (libc, -lc)

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.

ENOTTY
    fd refers to a file other than a terminal. On some older kernels, some types of files resulted in the error EINVAL in this case (which is a violation of POSIX, which specifies the error ENOTTY).

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value
 | Thread safety | MT-Safe

STANDARDS
POSIX.1-2008.

HISTORY
POSIX.1-2001, SVr4, 4.3BSD.

SEE ALSO
fstat(2), ttyname(3)