mirror of https://github.com/mkerrisk/man-pages
129 lines
3.2 KiB
Groff
129 lines
3.2 KiB
Groff
.\" Copyright (C) 2004 Michael Kerrisk
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH POSIX_OPENPT 3 2021-03-22 "" "Linux Programmer's Manual"
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.SH NAME
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posix_openpt \- open a pseudoterminal device
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.SH SYNOPSIS
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.nf
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.B #include <stdlib.h>
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.B #include <fcntl.h>
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.PP
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.BI "int posix_openpt(int " flags ");"
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.fi
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.PP
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.RS -4
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.RE
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.PP
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.BR posix_openpt ():
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.nf
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_XOPEN_SOURCE >= 600
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.fi
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.SH DESCRIPTION
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The
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.BR posix_openpt ()
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function opens an unused pseudoterminal master device, returning a
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file descriptor that can be used to refer to that device.
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.PP
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The
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.I flags
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argument is a bit mask that ORs together zero or more of
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the following flags:
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.TP
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.B O_RDWR
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Open the device for both reading and writing.
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It is usual to specify this flag.
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.TP
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.B O_NOCTTY
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Do not make this device the controlling terminal for the process.
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.SH RETURN VALUE
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On success,
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.BR posix_openpt ()
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returns a file descriptor (a nonnegative integer) which is the lowest
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numbered unused file descriptor.
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On failure, \-1 is returned, and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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See
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.BR open (2).
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.SH VERSIONS
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Glibc support for
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.BR posix_openpt ()
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has been provided since version 2.2.1.
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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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.ad l
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.nh
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.TS
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allbox;
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lbx 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 posix_openpt ()
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T} Thread safety MT-Safe
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.TE
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.hy
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.ad
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.sp 1
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008.
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.PP
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.BR posix_openpt ()
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is part of the UNIX 98 pseudoterminal support (see
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.BR pts (4)).
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.SH NOTES
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Some older UNIX implementations that support System V
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(aka UNIX 98) pseudoterminals don't have this function, but it
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can be easily implemented by opening the pseudoterminal multiplexor device:
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.PP
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.in +4n
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.EX
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int
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posix_openpt(int flags)
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{
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return open("/dev/ptmx", flags);
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}
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.EE
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.in
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.PP
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Calling
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.BR posix_openpt ()
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creates a pathname for the corresponding pseudoterminal slave device.
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The pathname of the slave device can be obtained using
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.BR ptsname (3).
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The slave device pathname exists only as long as the master device is open.
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.SH SEE ALSO
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.BR open (2),
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.BR getpt (3),
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.BR grantpt (3),
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.BR ptsname (3),
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.BR unlockpt (3),
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.BR pts (4),
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.BR pty (7)
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