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)