ttyname(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

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

NAME         top

       ttyname, ttyname_r - return name of a terminal

SYNOPSIS         top

       #include <unistd.h>

       char *ttyname(int fd);
       int ttyname_r(int fd, char *buf, size_t buflen);

DESCRIPTION         top

       The function ttyname() returns a pointer to the null-terminated
       pathname of the terminal device that is open on the file
       descriptor fd, or NULL on error (for example, if fd is not
       connected to a terminal).  The return value may point to static
       data, possibly overwritten by the next call.  The function
       ttyname_r() stores this pathname in the buffer buf of length
       buflen.

RETURN VALUE         top

       The function ttyname() returns a pointer to a pathname on
       success.  On error, NULL is returned, and errno is set to
       indicate the error.  The function ttyname_r() returns 0 on
       success, and an error number upon error.

ERRORS         top

       EBADF  Bad file descriptor.

       ENODEV fd refers to a slave pseudoterminal device but the
              corresponding pathname could not be found (see NOTES).

       ENOTTY fd does not refer to a terminal device.

       ERANGE (ttyname_r()) buflen was too small to allow storing the
              pathname.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌───────────────────────┬───────────────┬────────────────────────┐
       │Interface              Attribute     Value                  │
       ├───────────────────────┼───────────────┼────────────────────────┤
       │ttyname()              │ Thread safety │ MT-Unsafe race:ttyname │
       ├───────────────────────┼───────────────┼────────────────────────┤
       │ttyname_r()            │ Thread safety │ MT-Safe                │
       └───────────────────────┴───────────────┴────────────────────────┘

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, 4.2BSD.

NOTES         top

       A process that keeps a file descriptor that refers to a pts(4)
       device open when switching to another mount namespace that uses a
       different /dev/ptmx instance may still accidentally find that a
       device path of the same name for that file descriptor exists.
       However, this device path refers to a different device and thus
       can't be used to access the device that the file descriptor
       refers to.  Calling ttyname() or ttyname_r() on the file
       descriptor in the new mount namespace will cause these functions
       to return NULL and set errno to ENODEV.

SEE ALSO         top

       tty(1), fstat(2), ctermid(3), isatty(3), pts(4)

COLOPHON         top

       This page is part of release 5.12 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
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                     TTYNAME(3)

Pages that refer to this page: ctermid(3)getttyent(3)getutent(3)isatty(3)openpty(3)ptsname(3)ttyslot(3)