ttyname_r(3)

1ttyname(3)                 Library Functions Manual                 ttyname(3)
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NAME

6       ttyname, ttyname_r - return name of a terminal
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <unistd.h>
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14       char *ttyname(int fd);
15       int ttyname_r(int fd, char buf[.buflen], size_t buflen);
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DESCRIPTION

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

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

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

43       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
44       tributes(7).
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46       ┌─────────────────────────────┬───────────────┬────────────────────────┐
47       │Interface                    │ Attribute     │ Value                  │
48       ├─────────────────────────────┼───────────────┼────────────────────────┤
49       │ttyname()                    │ Thread safety │ MT-Unsafe race:ttyname │
50       ├─────────────────────────────┼───────────────┼────────────────────────┤
51       │ttyname_r()                  │ Thread safety │ MT-Safe                │
52       └─────────────────────────────┴───────────────┴────────────────────────┘
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STANDARDS

55       POSIX.1-2008.
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HISTORY

58       POSIX.1-2001, 4.2BSD.
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NOTES

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