man3/ttyname.3

   1 .\" Copyright (c) 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
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  24 .\" Modified 2001-12-13, Martin Schulze <joey@infodrom.org>
  25 .\" Added ttyname_r, aeb, 2002-07-20
  26 .\"
  27 .TH TTYNAME 3 2017-05-03 "Linux" "Linux Programmer's Manual"
  28 .SH NAME
  29 ttyname, ttyname_r \- return name of a terminal
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <unistd.h>
  33 .PP
  34 .BI "char *ttyname(int " fd );
  35 .PP
  36 .BI "int ttyname_r(int " fd ", char *" buf ", size_t " buflen );
  37 .fi
  38 .SH DESCRIPTION
  39 The function
  40 .BR ttyname ()
  41 returns a pointer to the null-terminated pathname of the terminal device
  42 that is open on the file descriptor \fIfd\fP, or NULL on error
  43 (for example, if \fIfd\fP is not connected to a terminal).
  44 The return value may point to static data, possibly overwritten by the
  45 next call.
  46 The function
  47 .BR ttyname_r ()
  48 stores this pathname in the buffer
  49 .I buf
  50 of length
  51 .IR buflen .
  52 .SH RETURN VALUE
  53 The function
  54 .BR ttyname ()
  55 returns a pointer to a pathname on success.
  56 On error, NULL is returned, and
  57 .I errno
  58 is set appropriately.
  59 The function
  60 .BR ttyname_r ()
  61 returns 0 on success, and an error number upon error.
  62 .SH ERRORS
  63 .TP
  64 .B EBADF
  65 Bad file descriptor.
  66 .TP
  67 .B ENOTTY
  68 File descriptor does not refer to a terminal device.
  69 .TP
  70 .B ERANGE
  71 .RB ( ttyname_r ())
  72 .I buflen
  73 was too small to allow storing the pathname.
  74 .TP
  75 .\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
  76 .B ENODEV
  77 File descriptor refers to a slave pseudoterminal device
  78 but the corresponding pathname could not be found (see NOTES).
  79 .SH ATTRIBUTES
  80 For an explanation of the terms used in this section, see
  81 .BR attributes (7).
  82 .TS
  83 allbox;
  84 lb lb lb
  85 l l l.
  86 Interface       Attribute       Value
  87 T{
  88 .BR ttyname ()
  89 T}      Thread safety   MT-Unsafe race:ttyname
  90 T{
  91 .BR ttyname_r ()
  92 T}      Thread safety   MT-Safe
  93 .TE
  94 .SH CONFORMING TO
  95 POSIX.1-2001, POSIX.1-2008, 4.2BSD.
  96 .SH NOTES
  97 A process that keeps a file descriptor that refers to a
  98 .BR pts (4)
  99 device open when switching to another mount namespace that uses a different
 100 .IR /dev/ptmx
 101 instance may still accidentally find that a device path of the same name
 102 for that file descriptor exists.
 103 However, this device path refers to a different device and thus
 104 can't be used to access the device that the file descriptor refers to.
 105 Calling
 106 .BR ttyname ()
 107 or
 108 .BR ttyname_r ()
 109 on the file descriptor in the new mount namespace will cause these
 110 functions to return NULL and set
 111 .I errno
 112 to
 113 .BR ENODEV .
 114 .SH SEE ALSO
 115 .BR tty (1),
 116 .BR fstat (2),
 117 .BR ctermid (3),
 118 .BR isatty (3),
 119 .BR pts (4)