isatty(3) — Linux manual page


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

NAME         top

       isatty - test whether a file descriptor refers to a terminal

SYNOPSIS         top

       #include <unistd.h>

       int isatty(int fd);

DESCRIPTION         top

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

RETURN VALUE         top

       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         top

       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         top

       For an explanation of the terms used in this section, see

       │Interface                             Attribute     Value   │
       │isatty()                              │ Thread safety │ MT-Safe │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

SEE ALSO         top

       fstat(2), ttyname(3)

COLOPHON         top

       This page is part of release 5.13 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

Linux                          2021-03-22                      ISATTY(3)

Pages that refer to this page: bash(1)ttyname(3)