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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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posix_openpt(3) Library Functions Manual posix_openpt(3)
posix_openpt - open a pseudoterminal device
Standard C library (libc, -lc)
#include <stdlib.h>
#include <fcntl.h>
int posix_openpt(int flags);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
posix_openpt():
_XOPEN_SOURCE >= 600
The posix_openpt() function opens an unused pseudoterminal master
device, returning a file descriptor that can be used to refer to
that device.
The flags argument is a bit mask that ORs together zero or more of
the following flags:
O_RDWR Open the device for both reading and writing. It is usual
to specify this flag.
O_NOCTTY
Do not make this device the controlling terminal for the
process.
On success, posix_openpt() returns a file descriptor (a
nonnegative integer) which is the lowest numbered unused file
descriptor. On failure, -1 is returned, and errno is set to
indicate the error.
See open(2).
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ posix_openpt() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
glibc 2.2.1. POSIX.1-2001.
It is part of the UNIX 98 pseudoterminal support (see pts(4)).
Some older UNIX implementations that support System V (aka UNIX
98) pseudoterminals don't have this function, but it can be easily
implemented by opening the pseudoterminal multiplexor device:
int
posix_openpt(int flags)
{
return open("/dev/ptmx", flags);
}
Calling posix_openpt() creates a pathname for the corresponding
pseudoterminal slave device. The pathname of the slave device can
be obtained using ptsname(3). The slave device pathname exists
only as long as the master device is open.
open(2), getpt(3), grantpt(3), ptsname(3), unlockpt(3), pts(4),
pty(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 posix_openpt(3)
Pages that refer to this page: getpt(3), grantpt(3), ptsname(3), unlockpt(3), org.freedesktop.machine1(5), pty(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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