posix_openpt(3) - Linux manual page (original) (raw)

posixopenpt(3) Library Functions Manual posixopenpt(3)

NAME top

   posix_openpt - open a pseudoterminal device

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#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 top

   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 top

   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](../man3/errno.3.html)_ is set to
   indicate the error.

ERRORS top

   See [open(2)](../man2/open.2.html).

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **posix_openpt**()                       │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   POSIX.1-2008.

HISTORY top

   glibc 2.2.1.  POSIX.1-2001.

   It is part of the UNIX 98 pseudoterminal support (see [pts(4)](../man4/pts.4.html)).

NOTES top

   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)](../man3/ptsname.3.html).  The slave device pathname exists
   only as long as the master device is open.

SEE ALSO top

   [open(2)](../man2/open.2.html), [getpt(3)](../man3/getpt.3.html), [grantpt(3)](../man3/grantpt.3.html), [ptsname(3)](../man3/ptsname.3.html), [unlockpt(3)](../man3/unlockpt.3.html), [pts(4)](../man4/pts.4.html),
   [pty(7)](../man7/pty.7.html)

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Linux man-pages 6.10 2024-07-23 posixopenpt(3)

Pages that refer to this page:getpt(3), grantpt(3), ptsname(3), unlockpt(3), org.freedesktop.machine1(5), pty(7)