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 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

       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 pathname.

ATTRIBUTES

       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

       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
       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

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

COLOPHON

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