man_3_isatty.txt

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 termi‐
       nal.

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 │
       └──────────┴───────────────┴─────────┘
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

SEE ALSO
       fstat(2), ttyname(3)

COLOPHON
       This page is part of release 5.05 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of this page, can  be
       found at https://www.kernel.org/doc/man-pages/.

Linux                                     2019-03-06                                 ISATTY(3)