1TTYNAME(3)                 Linux Programmer's Manual                TTYNAME(3)
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NAME

6       ttyname, ttyname_r - return name of a terminal
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SYNOPSIS

9       #include <unistd.h>
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11       char *ttyname(int fd);
12       int ttyname_r(int fd, char *buf, size_t buflen);
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DESCRIPTION

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

23       The function ttyname() returns a pointer to a pathname on success.   On
24       error,  NULL  is returned, and errno is set to indicate the error.  The
25       function ttyname_r() returns 0 on success, and an error number upon er‐
26       ror.
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ERRORS

29       EBADF  Bad file descriptor.
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31       ENODEV fd refers to a slave pseudoterminal device but the corresponding
32              pathname could not be found (see NOTES).
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34       ENOTTY fd does not refer to a terminal device.
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36       ERANGE (ttyname_r()) buflen was too small to allow  storing  the  path‐
37              name.
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ATTRIBUTES

40       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
41       tributes(7).
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43       ┌─────────────────────────────┬───────────────┬────────────────────────┐
44       │Interface                    │ Attribute     │ Value                  │
45       ├─────────────────────────────┼───────────────┼────────────────────────┤
46       │ttyname()                    │ Thread safety │ MT-Unsafe race:ttyname │
47       ├─────────────────────────────┼───────────────┼────────────────────────┤
48       │ttyname_r()                  │ Thread safety │ MT-Safe                │
49       └─────────────────────────────┴───────────────┴────────────────────────┘
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CONFORMING TO

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

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

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

68       This  page  is  part of release 5.12 of the Linux man-pages project.  A
69       description of the project, information about reporting bugs,  and  the
70       latest     version     of     this    page,    can    be    found    at
71       https://www.kernel.org/doc/man-pages/.
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75Linux                             2021-03-22                        TTYNAME(3)
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