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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.
Utilities & Libraries
C Library Reference
C
cnd_signal()
Unblock a thread that's waiting on a condition variable

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.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
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- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
  - C Library Reference
    - What's in a Function Description?
    - Manifests
    - Character Sets
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    - C
      - c16rtomb(), c32rtomb()
        Convert a wide character (UTF-16 or UTF-32) into a multibyte character (UTF-8)
      - _cred_info
        Structure that describes user and group credentials
      - cabs(), cabsf(), cabsl()
        Compute the absolute value of a complex number
      - cache_fini()
        Free cache-coherency resources when the driver is unloaded
      - CACHE_FLUSH()
        Flush cache lines associated with a data buffer
      - cache_init()
        Register with the cache-coherency library
      - CACHE_INVAL()
        Invalidate cache lines associated with a data buffer
      - CacheControl()
        Flush the data cache and/or invalidate the instruction and/or the data cache.
      - cacos(), cacosf(), cacosl()
        Compute the complex arc cosine
      - cacosh(), cacoshf(), cacoshl()
        Compute the complex inverse hyperbolic cosine
      - call_once()
        Dynamic package initialization
      - calloc()
        Allocate space for an array
      - carg(), cargf(), cargl()
        Compute the argument of a complex number
      - casin(), casinf(), casinl()
        Compute the complex arc sine
      - casinh(), casinhf(), casinhl()
        Compute the complex inverse hyperbolic sine
      - catan(), catanf(), catanl()
        Compute the complex arc tangent
      - catanh(), catanhf(), catanhl()
        Compute the complex inverse hyperbolic tangent
      - cbrt(), cbrtf(), cbrtl()
        Compute the cube root of a number
      - ccos(), ccosf(), ccosl()
        Compute the complex cosine
      - ccosh(), ccoshf(), ccoshl()
        Compute the complex hyperbolic cosine
      - ceil(), ceilf(), ceill()
        Round up a value to the next integer
      - cexp(), cexpf(), cexpl()
        Compute the complex base-e exponential of a complex number
      - cfgetispeed()
        Return the input baud rate that's stored in a termios structure
      - cfgetospeed()
        Return the output baud rate that's stored in a termios structure
      - cfmakeraw()
        Set terminal attributes
      - cfsetispeed()
        Set the input baud rate in a termios structure
      - cfsetospeed()
        Set the output baud rate in a termios structure
      - cfsetspeed()
        Set the input and output baud rates in a termios structure
      - ChannelCreate(), ChannelCreate_r(), ChannelCreatePulsePool()
        Create a communications channel
      - ChannelCtl(), ChannelCtl_r()
        Change the properties of a channel
      - ChannelDestroy(), ChannelDestroy_r()
        Destroy a communications channel
      - chdir()
        Change the current working directory
      - chmod()
        Change the permissions for a file
      - chown()
        Change the user ID and group ID of a file
      - chroot()
        Change the root directory
      - cimag(), cimagf(), cimagl()
        Compute the imaginary part of a complex number
      - clearenv()
        Clear the environment
      - clearerr()
        Clear a stream's end-of-file and error flags
      - clearsockprefix()
        Set to NULL the prefix for the networking stack path for the current thread
      - ClientInfoExtFree()
        Free the structure used for extended information about a client connection
      - clock()
        Return the number of clock ticks used by the program
      - clock_getcpuclockid()
        Return the clock ID of the CPU-time clock from a specified process
      - clock_getres()
        Get the resolution of the clock
      - clock_gettime()
        Get the current time of a clock
      - clock_gettime_ns(), clock_gettime_mon_ns(), clock_gettime_rt_ns()
        Get the time of a clock, in nanoseconds
      - clock_nanosleep()
        Suspend a thread until a timeout or signal occurs, using a specified clock
      - clock_settime()
        Set a clock
      - ClockAdjust(), ClockAdjust_r()
        Adjust the time of a clock
      - ClockCycles()
        Get the number of clock cycles
      - ClockId(), ClockId_r()
        Get the CPU-time clock ID for a given process and thread
      - ClockPeriod(), ClockPeriod_r()
        Get a clock period
      - ClockTime(), ClockTime_r()
        Get or set a clock
      - clog(), clogf(), clogl()
        Compute the complex natural (base-e) logarithm of a complex number
      - close()
        Close a file
      - closedir()
        Close a directory
      - closelog()
        Close the slogger2 system log
      - _cmdname()
        Find the path used to invoke the current process
      - CMPLX(), CMPLXF(), CMPLXL()
        Create a complex number from its real and imaginary parts
      - cnd_broadcast()
        Unblock threads waiting on a condition
      - cnd_destroy()
        Destroy a condition variable
      - cnd_init()
        Initialize a condition variable
      - cnd_signal()
        Unblock a thread that's waiting on a condition variable
      - cnd_timedwait()
        Wait on a condition variable, with a time limit
      - cnd_wait()
        Wait on a condition variable
      - confstr()
        Get configuration-defined string values
      - conj(), conjf(), conjl()
        Compute the complex conjugate of a complex number
      - ConnectAttach(), ConnectAttach_r()
        Establish a connection between a process and a channel
      - ConnectClientInfo(), ConnectClientInfo_r()
        Get information about a client connection
      - ConnectClientInfoAble()
        Get extended information about a client connection, including abilities
      - ConnectClientInfoExt()
        Get extended information about a client connection
      - ConnectDetach(), ConnectDetach_r()
        Break a connection between a process and a channel
      - ConnectDupFd(), ConnectDupFd_r()
        Support file descriptor duplication
      - ConnectFlags(), ConnectFlags_r()
        Modify or query the flags associated with a connection
      - ConnectServerInfo(), ConnectServerInfo_r()
        Get information about a server connection
      - copysign(), copysignf(), copysignl()
        Copy the sign bit from one number to another
      - cos(), cosf(), cosl()
        Compute the cosine of an angle
      - cosh(), coshf(), coshl()
        Compute the hyperbolic cosine
      - cpow(), cpowf(), cpowl()
        Raise a complex number to the power of another complex number
      - cproj(), cprojf(), cprojl()
        Compute the projection of a complex number on the Riemann sphere
      - creal(), crealf(), creall()
        Compute the real part of a complex number
      - creat(), creat64()
        Create and open a file (low-level)
      - crypt()
        Hash a password
      - csin(), csinf(), csinl()
        Compute the complex sine
      - csinh(), csinhf(), csinhl()
        Compute the complex hyperbolic sine
      - csqrt(), csqrtf(), csqrtl()
        Compute the square root of a complex number
      - ctan(), ctanf(), ctanl()
        Compute the complex tangent
      - ctanh(), ctanhf(), ctanhl()
        Compute the complex hyperbolic tangent
      - ctermid()
        Generate the path name of the current controlling terminal
      - ctime(), ctime_r()
        Convert calendar time to local time
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    - Full Safety Information
    - Glossary
  - Devctl and Ioctl Commands
  - JSON Library Reference
  - PAM Reference
  - QNX Helpers Developer's Guide
    These libraries provide QNX helpers, including helpers that assist with logging, string conversion, and number and type sizes.
  - SPI Framework Technote
  - QNX Cryptography Library
    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.
  - QNX devcrypto Service
  - 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.
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
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.

cnd_signal()

QNX SDP8.0C Library ReferenceAPIDeveloper

Unblock a thread that's waiting on a condition variable

Synopsis:

#include <threads.h>

int cnd_signal( cnd_t* cond );

Arguments:

cond: A pointer to the cnd_t object for which you want to unblock the highest-priority thread.

Library:

libc

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

Description:

The cnd_signal() function unblocks the highest priority thread that's waiting on the condition variable, cond. If more than one thread at the highest priority is waiting, cnd_signal() unblocks the one that has been waiting the longest.

Returns:

thrd_success: Success.
thrd_error: An error occurred.

Classification:

C11


Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Page updated: August 11, 2025