isatty(3) — Linux manual page

isatty(3)               Library Functions Manual               isatty(3)

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)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                      isatty(3)

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

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