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.

       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)

Linux                                                                          2021-03-22                                                                      ISATTY(3)