SYNOPSIS
       #define _XOPEN_SOURCE
       #include <stdlib.h>

       int unlockpt(int fd);

DESCRIPTION
       The  unlockpt() function unlocks the slave pseudo-terminal device (pty)
       corresponding to the master pty referred to by fd.

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

RETURN VALUE
       When successful, unlockpt() returns 0.  Otherwise, it  returns  -1  and
       sets errno appropriately.

ERRORS
       EBADF  The fd argument is not a file descriptor open for writing.

       EINVAL The fd argument is not associated with a master pty.

VERSIONS
       unlockpt() is provided in glibc since version 2.1.

CONFORMING TO
       POSIX.1-2001.

SEE ALSO
       grantpt(3),      posix_openpt(3),      ptsname(3),     pts(4),     fea-
       ture_test_macros(7), pty(7)

COLOPHON
       This page is part of release 3.23 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.