unlockpt(3p)

unlockpt3p

Unlock a pseudo-terminal master/slave pair

Usage

#include <stdlib.h>

int unlockpt(int fildes);

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Overview

The unlockpt() function shall unlock the slave pseudo-terminal device associated with the master to which fildes refers.

Conforming applications shall ensure that they call unlockpt() before opening the slave side of a pseudo-terminal device.

Return value

Upon successful completion, unlockpt() shall return 0. Otherwise, it shall return -1 and set errno to indicate the error.

Errors

The unlockpt() function may fail if:

EBADF

The fildes argument is not a file descriptor open for writing.

EINVAL

The fildes argument is not associated with a master pseudo-terminal device.

The following sections are informative.

Examples

None.

Application usage

None.

Rationale

See the RATIONALE section for posix_openpt().

Future directions

None.

From man-pages 6.19-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.