posix_openpt (3)

#include <stdlib.h>
#include <fcntl.h>

int posix_openpt(int flags);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

posix_openpt(): _XOPEN_SOURCE >= 600

The posix_openpt() function opens an unused pseudoterminal master device, returning a file descriptor that can be used to refer to that device.

The flags argument is a bit mask that ORs together zero or more of the following flags:

O_RDWR

Open the device for both reading and writing. It is usual to specify this flag.

O_NOCTTY

Do not make this device the controlling terminal for the process.

On success, posix_openpt() returns a nonnegative file descriptor which is the lowest numbered unused descriptor. On failure, -1 is returned, and errno is set to indicate the error.

See open(2).

Glibc support for posix_openpt() has been provided since version 2.2.1.

Multithreading (see pthreads(7))

The posix_openpt() function is thread-safe.

posix_openpt() is part of the UNIX 98 pseudoterminal support (see pts(4)). This function is specified in POSIX.1-2001.

The posix_openpt() function is a recent invention in POSIX. Some UNIX implementations that support System V (aka UNIX 98) pseudoterminals don't have this function, but it is easy to implement:

int
posix_openpt(int flags)
{
    return open("/dev/ptmx", flags);
}

Calling posix_openpt() creates a pathname for the corresponding pseudoterminal slave device. The pathname of the slave device can be obtained using ptsname(3). The slave device pathname exists only as long as the master device is open.

open(2), getpt(3), grantpt(3), ptsname(3), unlockpt(3), pts(4), pty(7)

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