ttyname_r

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

NAME
       ttyname, ttyname_r - return name of a terminal

SYNOPSIS
       #include <unistd.h>

       char *ttyname(int fd);

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

DESCRIPTION
       The  function  ttyname() returns a pointer to the null-terminated path-
       name 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
       The function ttyname() returns a pointer to a pathname on success.   On
       error,  NULL is returned, and errno is set appropriately.  The function
       ttyname_r() returns 0 on success, and an error number upon error.

ERRORS
       EBADF  Bad file descriptor.

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

       ENOTTY File descriptor does not refer to a terminal device.

       ERANGE (ttyname_r())  buflen  was  too small to allow storing the path-
              name.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(7).

       +------------+---------------+------------------------+
       |Interface   | Attribute     | Value                  |
       +------------+---------------+------------------------+
       |ttyname()   | Thread safety | MT-Unsafe race:ttyname |
       +------------+---------------+------------------------+
       |ttyname_r() | Thread safety | MT-Safe                |
       +------------+---------------+------------------------+
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, 4.2BSD.

NOTES
       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  tty-
       name_r()  on  the file descriptor in the new mount namespace will cause
       these functions to return NULL and set errno to ENODEV.

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

COLOPHON
       This page is part of release 5.05 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                             2019-10-10                        TTYNAME(3)