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)):

    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.

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