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posix_openpt()
Open a pseudo-terminal device

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
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  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
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  - C Library Reference
    - What's in a Function Description?
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      - pathconf()
        Return the value of a configurable limit
      - pathfind(), pathfind_r()
        Search for a file in a list of directories
      - pathmgr_link()
        Create a node in the path space that represents the mountpoint of a device or filesystem
      - pathmgr_symlink()
        Create a procmgr symlink
      - pathmgr_unlink()
        Remove a link
      - pause()
        Suspend the calling thread until it runs a signal handler
      - _PAYLOAD_OF()
        Generate a pointer to the payload that follows the specified header member of an object
      - pci_*()
        Connect to the PCI server
      - pclose()
        Close a pipe
      - perror()
        Print an error message associated with errno
      - pipe()
        Create a pipe
      - pipe2()
        Create a pipe with additional control flags.
      - poll()
        Multiplex input/output over a set of file descriptors
      - popen()
        Execute a command, creating a pipe to it
      - posix_devctl()
        Control a device
      - posix_fadvise(), posix_fadvise64()
        Provide advisory information about the expected use of a file
      - posix_fallocate(), posix_fallocate64()
        Allocate space for a file on the filesystem
      - posix_madvise()
        Provide advisory information about the expected use of memory
      - posix_mem_offset(), posix_mem_offset64()
        Get the physical address and length of a mapped memory block
      - posix_memalign()
        Allocate aligned memory
      - posix_openpt()
        Open a pseudo-terminal device
      - posix_spawn(), posix_spawnp()
        Spawn a process
      - posix_spawn_file_actions_addclose()
        Add a close a file descriptor action to a spawn file actions object
      - posix_spawn_file_actions_adddup2()
        Add a duplicate a file descriptor action to a spawn file actions object
      - posix_spawn_file_actions_addopen()
        Add an open a file action to a spawn file action object
      - posix_spawn_file_actions_destroy()
        Destroy a spawn file actions object
      - posix_spawn_file_actions_init()
        Initialize a spawn file actions object
      - posix_spawnattr_destroy()
        Destroy a spawn attributes object
      - posix_spawnattr_getaslr()
        Return the address space layout randomization (ASLR) setting from a posix_spawn() attribute structure
      - posix_spawnattr_getcred()
        Get the user and group ID attributes from a spawn attributes object
      - posix_spawnattr_getflags()
        Get the POSIX flags from a spawn attributes object
      - posix_spawnattr_getpgroup()
        Get the process group attribute of a spawn attributes object
      - posix_spawnattr_getrunmask()
        Get the runmask attribute from a spawn attributes object
      - posix_spawnattr_getschedparam()
        Get the scheduling parameters attribute of a spawn attributes object
      - posix_spawnattr_getschedpolicy()
        Get the scheduling policy attribute of a spawn attributes object
      - posix_spawnattr_getsigdefault()
        Get the default signals attribute of a spawn attributes object
      - posix_spawnattr_getsigignore()
        Get the ignored signals attribute from a spawn attributes object
      - posix_spawnattr_getsigmask()
        Get the signal mask attribute of a spawn attributes object
      - posix_spawnattr_getstackmax()
        Get the maximum stack size attribute from a spawn attributes object
      - posix_spawnattr_gettypeid()
        Get the type identifier of a spawn attributes object
      - posix_spawnattr_getxflags()
        Get the POSIX flags and the QNX OS extended flags from a spawn attributes object
      - posix_spawnattr_init()
        Initialize a spawn attributes object
      - posix_spawnattr_setasid()
        Set the address space ID attribute in a spawn attributes object
      - posix_spawnattr_setaslr()
        Control how the address space layout randomization (ASLR) setting of a child is determined
      - posix_spawnattr_setcred()
        Set the user and group ID attributes in a spawn attributes object
      - posix_spawnattr_setcwd_np()
        Set the current working directory attribute in a spawn attributes object
      - posix_spawnattr_setflags()
        Set the POSIX flags in a spawn attributes object
      - posix_spawnattr_setpgroup()
        Set the process group attribute in a spawn attributes object
      - posix_spawnattr_setrunmask()
        Set the runmask attribute in a spawn attributes object
      - posix_spawnattr_setschedparam()
        Set the scheduling parameters attribute of a spawn attributes object
      - posix_spawnattr_setschedpolicy()
        Set the scheduling policy attribute of a spawn attributes object
      - posix_spawnattr_setsigdefault()
        Set the default signals attribute of a spawn attributes object
      - posix_spawnattr_setsigignore()
        Set the ignored signals attribute of a spawn attributes object
      - posix_spawnattr_setsigmask()
        Set the signal mask attribute of a spawn attributes object
      - posix_spawnattr_setstackmax()
        Set the maximum stack size attribute in a spawn attributes object
      - posix_spawnattr_settypeid()
        Set the type identifier of a spawn attributes object
      - posix_spawnattr_setxflags()
        Set the POSIX flags and the QNX OS extended flags in a spawn attributes object
      - posix_typed_mem_get_info()
        Get information about a typed memory object
      - posix_typed_mem_open()
        Open a typed memory object
      - pow(), powf(), powl()
        Raise a number to a given power
      - pread(), pread64()
        Read from a file without moving the file pointer
      - printf()
        Write formatted output to stdout
      - prlimit(), prlimit64()
        Set and get the limit on a system resource
      - procmgr_ability()
        Control a process's ability to perform certain operations
      - procmgr_ability_create()
        Create a process-manager ability
      - procmgr_ability_lookup()
        Look up a process-manager ability
      - procmgr_ability_name()
        Get the name of a custom ability
      - procmgr_daemon()
        Run a process in the background
      - procmgr_event_notify()
        Ask to be notified of system-wide events
      - procmgr_event_notify_add()
        Add a request to be notified of system-wide events
      - procmgr_event_notify_delete()
        Delete a request to be notified of system-wide events
      - procmgr_event_trigger(), procmgr_event_trigger_updateable()
        Trigger a system-wide event
      - procmgr_session(), procmgr_session_ext()
        Provide process manager session support
      - procmgr_set_type_id()
        Allows a function to change its own type identifier
      - procmgr_timer_tolerance()
        Get or set the default timer tolerance for a process
      - procmgr_value_current()
        Get the current value of an item being monitored
      - procmgr_value_notify_add()
        Add an event to be triggered when a monitored value crosses a trigger point
      - __progname
        The basename of the program being executed
      - pthread_abort()
        Unconditionally terminate the target thread
      - pthread_atfork()
        Register fork handlers
      - pthread_attr_destroy()
        Destroy a thread-attribute object
      - pthread_attr_getdefaultguardsize()
        Get the default stack guard area size
      - pthread_attr_getdefaultstacksize()
        Get the default stack size
      - pthread_attr_getdetachstate()
        Get the thread detach state attribute
      - pthread_attr_getguardsize()
        Get the size of the thread's guard area
      - pthread_attr_getinheritsched()
        Get a thread's inherit-scheduling attribute
      - pthread_attr_getschedparam()
        Get the thread scheduling parameters attribute
      - pthread_attr_getschedpolicy()
        Get the thread scheduling policy attribute
      - pthread_attr_getscope()
        Get the thread contention scope attribute
      - pthread_attr_getstack()
        Get the thread-creation stack attributes
      - pthread_attr_getstackaddr()
        Get the thread stack address attribute
      - pthread_attr_getstacklazy()
        Get the thread lazy-stack attribute
      - pthread_attr_getstackprealloc()
        Get the amount of memory to preallocate for a thread's MAP_LAZY stack
      - pthread_attr_getstacksize()
        Get the thread stack-size attribute
      - pthread_attr_getsuspendstate_np()
        Get the thread suspend state attribute
      - pthread_attr_init()
        Initialize a thread-attribute object
      - pthread_attr_setdefaultguardsize()
        Set the default stack guard area size
      - pthread_attr_setdefaultstacksize()
        Set the default stack size
      - pthread_attr_setdetachstate()
        Set the thread detach state attribute
      - pthread_attr_setguardsize()
        Set the size of the thread's guard area
      - pthread_attr_setinheritsched()
        Set the thread's inherit-scheduling attribute
      - pthread_attr_setschedparam()
        Set a thread's scheduling parameters attribute
      - pthread_attr_setschedpolicy()
        Set the thread scheduling policy attribute
      - pthread_attr_setscope()
        Set the thread contention scope attribute
      - pthread_attr_setstack()
        Set the thread-creation stack attributes
      - pthread_attr_setstackaddr()
        Set the thread stack address attribute
      - pthread_attr_setstacklazy()
        Set the thread lazy-stack attribute
      - pthread_attr_setstackprealloc()
        Set the amount of memory to preallocate for a thread's MAP_LAZY stack
      - pthread_attr_setstacksize()
        Set the thread stack-size attribute
      - pthread_attr_setsuspendstate_np()
        Set the thread suspend state attribute
      - pthread_barrier_destroy()
        Destroy a barrier object
      - pthread_barrier_init()
        Initialize a barrier object
      - pthread_barrier_wait()
        Synchronize participating threads at the barrier
      - pthread_barrierattr_destroy()
        Destroy a barrier-attributes object
      - pthread_barrierattr_getpshared()
        Get the value of a barrier's process-shared attribute
      - pthread_barrierattr_init()
        Initialize a barrier attributes object
      - pthread_barrierattr_setpshared()
        Set the value of a barrier's process-shared attribute
      - pthread_cancel()
        Cancel a thread
      - pthread_cleanup_pop()
        Pop a function off of a thread's cancellation-cleanup stack
      - pthread_cleanup_push()
        Push a function onto a thread's cancellation-cleanup stack
      - pthread_cluster_get_runmask()
        Validate a cluster name and provide its associated runmask
      - pthread_cluster_set()
        Set cluster characteristics for the calling thread
      - pthread_cluster_set_and_inherit()
        Set cluster characteristics for the calling thread and for its children to inherit
      - pthread_cond_broadcast()
        Unblock threads waiting on a condition
      - pthread_cond_clockwait()
        Wait on a condition variable, with a time limit measured against a specific clock
      - pthread_cond_destroy()
        Destroy a condition variable
      - pthread_cond_init()
        Initialize a condition variable
      - pthread_cond_signal()
        Unblock a thread that's waiting on a condition variable
      - pthread_cond_timedwait()
        Wait on a condition variable, with a time limit
      - pthread_cond_wait()
        Wait on a condition variable
      - pthread_condattr_destroy()
        Destroy a condition-variable attribute object
      - pthread_condattr_getclock()
        Get the clock attribute from a condition-variable attribute object
      - pthread_condattr_getpshared()
        Get the process-shared attribute from a condition variable attribute object
      - pthread_condattr_init()
        Initialize the attribute object for creating condition variables
      - pthread_condattr_setclock()
        Set the clock attribute of a condition-variable attribute object
      - pthread_condattr_setpshared()
        Set the process-shared attribute in a condition variable attribute object
      - pthread_create()
        Create a thread
      - pthread_detach()
        Detach a thread from a process
      - pthread_equal()
        Compare two thread IDs
      - pthread_exit()
        Terminate a thread
      - pthread_getconcurrency()
        Get the level of thread concurrency
      - pthread_getcpuclockid()
        Return the clock ID of the CPU-time clock from a specified thread
      - pthread_getname_np()
        Retrieve the name of a thread
      - pthread_getschedparam()
        Get a thread's scheduling parameters
      - pthread_getspecific()
        Get a thread-specific data value
      - pthread_join()
        Join thread
      - pthread_key_create()
        Create a thread-specific data key
      - pthread_key_delete()
        Delete a thread-specific data key
      - pthread_kill()
        Send a signal to a thread
      - pthread_mutex_clocklock()
        Lock a mutex with a time limit measured against a specific clock
      - pthread_mutex_consistent()
        Mark as consistent the state that's protected by a mutex
      - pthread_mutex_destroy()
        Destroy a mutex
      - pthread_mutex_getprioceiling()
        Get a mutex's priority ceiling
      - pthread_mutex_init()
        Initialize a mutex
      - pthread_mutex_lock()
        Lock a mutex
      - pthread_mutex_setprioceiling()
        Set a mutex's priority ceiling
      - pthread_mutex_timedlock(), pthread_mutex_timedlock_monotonic()
        Lock a mutex, with a time limit
      - pthread_mutex_trylock()
        Attempt to lock a mutex
      - pthread_mutex_unlock()
        Unlock a mutex
      - pthread_mutex_wakeup_np()
        Unblock any threads that are waiting on a mutex
      - pthread_mutexattr_destroy()
        Destroy mutex attribute object
      - pthread_mutexattr_getprioceiling()
        Get the priority ceiling of a mutex attribute object
      - pthread_mutexattr_getprotocol()
        Get a mutex's scheduling protocol
      - pthread_mutexattr_getpshared()
        Get the process-shared attribute from a mutex attribute object
      - pthread_mutexattr_getrecursive()
        Get the recursive attribute from a mutex attribute object
      - pthread_mutexattr_getrobust()
        Get the robust attribute from a mutex attribute object
      - pthread_mutexattr_gettype()
        Get a mutex type
      - pthread_mutexattr_getwakeup_np()
        Get the wake-up attribute of a mutex
      - pthread_mutexattr_init()
        Initialize a mutex attribute object
      - pthread_mutexattr_setprioceiling()
        Set the priority ceiling of a mutex attribute object
      - pthread_mutexattr_setprotocol()
        Set a mutex's scheduling protocol
      - pthread_mutexattr_setpshared()
        Set the process-shared attribute in mutex attribute object
      - pthread_mutexattr_setrecursive()
        Set the recursive attribute in mutex attribute object
      - pthread_mutexattr_setrobust()
        Set the robust attribute in a mutex attribute object
      - pthread_mutexattr_settype()
        Set a mutex type
      - pthread_mutexattr_setwakeup_np()
        Set the wake-up attribute of a mutex
      - pthread_once()
        Dynamic package initialization
      - pthread_rwlock_clockrdlock()
        Lock a read-write lock for reading with a time limit measured against a clock
      - pthread_rwlock_clockwrlock()
        Lock a read-write lock for writing with a time limit measured against a specific clock
      - pthread_rwlock_destroy()
        Destroy a read-write lock
      - pthread_rwlock_init()
        Initialize a read-write lock
      - pthread_rwlock_rdlock()
        Acquire a shared read lock on a read-write lock
      - pthread_rwlock_timedrdlock()
        Lock a read-write lock for reading
      - pthread_rwlock_timedwrlock()
        Lock a read-write lock for writing
      - pthread_rwlock_tryrdlock()
        Attempt to acquire a shared lock on a read-write lock
      - pthread_rwlock_trywrlock()
        Attempt to acquire an exclusive lock on a read-write lock
      - pthread_rwlock_unlock()
        Unlock a read-write lock
      - pthread_rwlock_wrlock()
        Acquire an exclusive write lock on a read-write lock
      - pthread_rwlockattr_destroy()
        Destroy a read-write lock attribute object
      - pthread_rwlockattr_getpshared()
        Get the process-shared attribute of a read-write lock attribute object
      - pthread_rwlockattr_init()
        Create a read-write lock attribute object
      - pthread_rwlockattr_setpshared()
        Set the process-shared attribute of a read-write lock attribute object
      - pthread_self()
        Get the calling thread's ID
      - pthread_setcancelstate()
        Set a thread's cancellation state
      - pthread_setcanceltype()
        Set a thread's cancellation type
      - pthread_setconcurrency()
        Set the concurrency level for a thread
      - pthread_setname_np()
        Name a thread
      - pthread_setschedparam()
        Set thread scheduling parameters
      - pthread_setschedprio()
        Set a thread's priority
      - pthread_setspecific()
        Set a thread-specific data value
      - pthread_sigmask()
        Modify or examine a thread's signal-blocked mask
      - pthread_spawnattr_getrunmask_np()
        Get the 64-bit runmask attribute from a spawn attributes object
      - pthread_spawnattr_setrunmask_np()
        Set the 64-bit runmask attribute in a spawn attributes object
      - pthread_spin_destroy()
        Destroy a thread spinlock
      - pthread_spin_init()
        Initialize a thread spinlock
      - pthread_spin_lock()
        Lock a thread spinlock
      - pthread_spin_trylock()
        Try to lock a thread spinlock
      - pthread_spin_unlock()
        Unlock a thread spinlock
      - pthread_testcancel()
        Test thread cancellation
      - pthread_timedjoin(), pthread_timedjoin_monotonic()
        Join a thread, with a time limit
      - ptsname()
        Get the name of a slave pseudo-terminal device
      - ptsname_r()
        Get the name of a slave pseudo-terminal device
      - _pulse
        Structure that describes a pulse
      - pulse_attach()
        Attach a handler function to a pulse code
      - pulse_detach()
        Detach a handler function from a pulse code
      - putc()
        Write a character to a stream
      - putc_unlocked()
        Write a character to an output stream
      - putchar()
        Write a character to standard output
      - putchar_unlocked()
        Write a character to stdout
      - putenv()
        Add, change or delete an environment variable
      - puts()
        Write a string to stdout
      - putspent()
        Put an entry into the shadow password database
      - pututline()
        Write an entry in the user-information file
      - putw()
        Put a word on a stream
      - putwc()
        Write a wide character to a stream
      - putwchar()
        Write a wide character to a stdout
      - pwrite(), pwrite64()
        Write into a file without changing the file pointer
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    These libraries provide QNX helpers, including helpers that assist with logging, string conversion, and number and type sizes.
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    The QNX Cryptography Library (qcrypto) is a flexible cryptography framework that allows you to choose which cryptography provider responds to requests on a per-process basis.
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  - Utilities Reference
  - WPA Control Interface Reference
    This document provides a reference for the Wi-Fi Protected Access (WPA) control interface, which provides a C API for the WPA/IEEE 802.11i protocols in Wi-Fi client stations. Application developers who want to control WPA operations and get associated status and event data should read this reference.
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This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

posix_openpt()

QNX SDP8.0C Library ReferenceAPIDeveloper

Open a pseudo-terminal device

Synopsis:

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

int posix_openpt( int oflag );

Arguments:

oflag

Flags that specify the file status flags and file access modes of the open file description; a combination of the following:

O_RDWR — open for reading and writing.
O_NOCTTY — don't make the terminal device become the controlling terminal for the process.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The posix_openpt() function establishes a connection between a master device for a pseudo-terminal and a file descriptor. The file descriptor is used by other I/O functions that refer to that pseudo-terminal.

Returns:

A file descriptor for the master pseudo-terminal, or -1 if an error occurred (errno is set).

Errors:

EMFILE: All file descriptors available to the process are currently open.
ENFILE: The maximum allowable number of files is currently open in the system.
EINVAL: The value of oflag isn't valid.
EAGAIN: Out of pseudo-terminal resources.

Classification:

POSIX 1003.1 XSI


Safety:
Cancellation point	Yes
Signal handler	Yes
Thread	Yes

Page updated: August 11, 2025