isatty(3)                  Library Functions Manual                  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   |
       +--------------------------------------------+---------------+---------+
       |isatty ()                                   | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       POSIX.1-2008.

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

SEE ALSO
       fstat(2), ttyname(3)

Linux man-pages 6.7               2023-10-31                         isatty(3)