NAME

unlockpt — unlock a pseudo-terminal device pair

SYNOPSIS

#include <stdlib.h>

int
unlockpt(int fildes);

DESCRIPTION

When a pseudo-terminal manager device is opened, whether through posix_openpt(3C) or open(2) on a ptm(4D) device, the subsidiary device begins operation in a locked state. The unlockpt() function unlocks the pseudo-terminal subsidiary device associated with the manager device to which fildes refers.

Portable applications must call unlockpt() before opening the pseudo-terminal subsidiary device.

RETURN VALUES

The unlockpt() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

EXAMPLES

See posix_openpt(3C) for an example that includes a call to unlockpt().

ERRORS

The unlockpt() function may fail if:

EBADF

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

EINVAL

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

INTERFACE STABILITY

Committed

MT LEVEL

Safe

SEE ALSO

open(2), grantpt(3C), posix_openpt(3C), ptsname(3C), ptm(4D), attributes(7), standards(7)