unlockpt man page


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.

unlockpt — unlock a pseudo-terminal master/slave pair


#include <stdlib.h>

int unlockpt(int fildes);


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.


The unlockpt() function may fail if:

The fildes argument is not a file descriptor open for writing.
The fildes argument is not associated with a master pseudo-terminal device.

The following sections are informative.


See the Rationale section for posix_openpt().

See Also

grantpt(), open(), posix_openpt(), ptsname()

The Base Definitions volume of POSIX.1‐2008, <stdlib.h>


2013 IEEE/The Open Group POSIX Programmer's Manual