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posix_openpt(3) — Linux manual page

posix_openpt(3)          Library Functions Manualposix_openpt(3)

NAME        top

       posix_openpt - open a pseudoterminal device

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <stdlib.h>#include <fcntl.h>int posix_openpt(intflags);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):posix_openpt():           _XOPEN_SOURCE >= 600

DESCRIPTION        top

       Theposix_openpt() function opens an unused pseudoterminal master       device, returning a file descriptor that can be used to refer to       that device.       Theflags argument is a bit mask that ORs together zero or more of       the following flags:O_RDWROpen 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.

RETURN VALUE        top

       On success,posix_openpt() returns a file descriptor (a       nonnegative integer) which is the lowest numbered unused file       descriptor.  On failure, -1 is returned, anderrno is set to       indicate the error.

ERRORS        top

       Seeopen(2).

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │posix_openpt()                       │ Thread safety │ MT-Safe │       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS        top

       POSIX.1-2008.

HISTORY        top

       glibc 2.2.1.  POSIX.1-2001.       It is part of the UNIX 98 pseudoterminal support (seepts(4)).

NOTES        top

       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);           }       Callingposix_openpt() creates a pathname for the corresponding       pseudoterminal slave device.  The pathname of the slave device can       be obtained usingptsname(3).  The slave device pathname exists       only as long as the master device is open.

SEE ALSO        top

open(2),getpt(3),grantpt(3),ptsname(3),unlockpt(3),pts(4),pty(7)

COLOPHON        top

       This page is part of theman-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 isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17posix_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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