UNLOCKPT(3) Linux Programmer's Manual UNLOCKPT(3)

unlockpt - unlock a pseudoterminal master/slave pair

#define _XOPEN_SOURCE
#include <stdlib.h>
int unlockpt(int fd);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

unlockpt():

Since glibc 2.24:
    _XOPEN_SOURCE >= 500
Glibc 2.23 and earlier:
    _XOPEN_SOURCE

The unlockpt() function unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by the file descriptor fd.

unlockpt() should be called before opening the slave side of a pseudoterminal.

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

EBADF
The fd argument is not a file descriptor open for writing.
EINVAL
The fd argument is not associated with a master pseudoterminal.

unlockpt() is provided in glibc since version 2.1.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
unlockpt () Thread safety MT-Safe

POSIX.1-2001, POSIX.1-2008.

grantpt(3), posix_openpt(3), ptsname(3), pts(4), pty(7)

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2021-03-22