posix_openpt - Man Page

open a pseudoterminal device

Library

Standard C library (libc, -lc)

Synopsis

#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

Description

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.

Return Value

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

Errors

See open(2).

Versions

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

Attributes

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

InterfaceAttributeValue
posix_openpt()Thread safetyMT-Safe

Standards

POSIX.1-2001, POSIX.1-2008.

posix_openpt() is part of the UNIX 98 pseudoterminal support (see pts(4)).

Notes

Some older UNIX implementations that support System V (aka UNIX 98) pseudoterminals don't have this function, but it can be easily implemented by opening the pseudoterminal multiplexor device:

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.

See Also

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

Referenced By

getpt(3), grantpt(3), org.freedesktop.machine1(5), ptsname(3), pty(7), unlockpt(3).

2022-10-09 Linux man-pages 6.01