mirror of https://github.com/mkerrisk/man-pages
122 lines
3.3 KiB
Groff
122 lines
3.3 KiB
Groff
.\" Copyright (c) 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" Modified 2001-12-13, Martin Schulze <joey@infodrom.org>
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.\" Added ttyname_r, aeb, 2002-07-20
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.\"
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.TH TTYNAME 3 2019-10-10 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ttyname, ttyname_r \- return name of a terminal
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.SH SYNOPSIS
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.nf
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.B #include <unistd.h>
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.PP
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.BI "char *ttyname(int " fd );
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.PP
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.BI "int ttyname_r(int " fd ", char *" buf ", size_t " buflen );
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.fi
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.SH DESCRIPTION
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The function
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.BR ttyname ()
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returns a pointer to the null-terminated pathname of the terminal device
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that is open on the file descriptor \fIfd\fP, or NULL on error
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(for example, if \fIfd\fP is not connected to a terminal).
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The return value may point to static data, possibly overwritten by the
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next call.
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The function
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.BR ttyname_r ()
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stores this pathname in the buffer
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.I buf
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of length
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.IR buflen .
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.SH RETURN VALUE
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The function
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.BR ttyname ()
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returns a pointer to a pathname on success.
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On error, NULL is returned, and
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.I errno
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is set appropriately.
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The function
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.BR ttyname_r ()
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returns 0 on success, and an error number upon error.
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.SH ERRORS
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.TP
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.B EBADF
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Bad file descriptor.
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.TP
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.\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
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.B ENODEV
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.I fd
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refers to a slave pseudoterminal device
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but the corresponding pathname could not be found (see NOTES).
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.TP
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.B ENOTTY
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.I fd
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does not refer to a terminal device.
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.TP
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.B ERANGE
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.RB ( ttyname_r ())
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.I buflen
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was too small to allow storing the pathname.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR ttyname ()
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T} Thread safety MT-Unsafe race:ttyname
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T{
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.BR ttyname_r ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008, 4.2BSD.
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.SH NOTES
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A process that keeps a file descriptor that refers to a
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.BR pts (4)
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device open when switching to another mount namespace that uses a different
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.I /dev/ptmx
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instance may still accidentally find that a device path of the same name
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for that file descriptor exists.
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However, this device path refers to a different device and thus
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can't be used to access the device that the file descriptor refers to.
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Calling
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.BR ttyname ()
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or
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.BR ttyname_r ()
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on the file descriptor in the new mount namespace will cause these
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functions to return NULL and set
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.I errno
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to
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.BR ENODEV .
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.SH SEE ALSO
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.BR tty (1),
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.BR fstat (2),
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.BR ctermid (3),
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.BR isatty (3),
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.BR pts (4)
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