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unlockpt(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|ATTRIBUTES \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

unlockpt(3)              Library Functions Manualunlockpt(3)

NAME top

       unlockpt - unlock a pseudoterminal master/slave pair

LIBRARY top

       Standard C library (libc,-lc)

SYNOPSIS top

#define _XOPEN_SOURCE#include <stdlib.h>int unlockpt(intfd);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):unlockpt():           Since glibc 2.24:               _XOPEN_SOURCE >= 500           glibc 2.23 and earlier:               _XOPEN_SOURCE

DESCRIPTION top

       Theunlockpt() function unlocks the slave pseudoterminal device       corresponding to the master pseudoterminal referred to by the file       descriptorfd.unlockpt() should be called before opening the slave side of a       pseudoterminal.

RETURN VALUE top

       When successful,unlockpt() returns 0.  Otherwise, it returns -1       and setserrno to indicate the error.

ERRORS top

EBADFThefd argument is not a file descriptor open for writing.EINVALThefd argument is not associated with a master              pseudoterminal.

ATTRIBUTES top

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

STANDARDS top

       POSIX.1-2008.

HISTORY top

       glibc 2.1.  POSIX.1-2001.

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            2024-07-23unlockpt(3)

Pages that refer to this page:TIOCPKT(2const), getpt(3), grantpt(3), posix_openpt(3), ptsname(3), pts(4), pty(7)

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