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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).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │isatty()                                                                      │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001, SVr4, 4.3BSD.

SEE ALSO

       fstat(2), ttyname(3)