unlockpt(3) - BetterMan

unlockpt(3)

unlock a pseudoterminal master/slave pair

distropkg manpages-dev@6.9.1-1dataset 2026-04-01T06:19:02Z+debian+ec4110e+mandoc:1.14.6-4

Synopsis

#define _XOPEN_SOURCE
#include <stdlib.h>
int unlockpt(int 
fd
);
unlockpt
():
Since glibc 2.24:
        _XOPEN_SOURCE >= 500
    glibc 2.23 and earlier:
        _XOPEN_SOURCE

—

Options · 2

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

NAME

unlockpt - unlock a pseudoterminal master/slave pair

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

bash

#define _XOPEN_SOURCE\n
\n#include <stdlib.h>

bash

int unlockpt(int \nfd\n);

unlockpt():

bash


\n
    Since glibc 2.24:
\n
        _XOPEN_SOURCE >= 500
\n
    glibc 2.23 and earlier:
\n
        _XOPEN_SOURCE

DESCRIPTION

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.

RETURN VALUE

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

ERRORS

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

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
unlockpt ()	Thread safety	MT-Safe

STANDARDS

POSIX.1-2008.

HISTORY

glibc 2.1. POSIX.1-2001.