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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 QNX Neutrino 7.1.
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C Library Reference
H
h_errno
Host error variable

QNX Momentics IDE User's Guide
This User's Guide describes version 7.1 of the Integrated Development Environment (IDE) that's part of the QNX Momentics 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 QNX Neutrino 7.1.
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  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX Neutrino RTOS system and developers who want to create a QNX Neutrino resource manager free from vulnerabilities.
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  - Addon Interfaces Library Reference
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      - h_errno
        Host error variable
      - hcreate()
        Create a hash search table
      - hdestroy()
        Destroy the hash search table
      - herror()
        Print the message associated with the value of h_errno to standard error
      - hostent
        Structure that describes an Internet host
      - hsearch()
        Search the hash search table
      - hstrerror()
        Get an error message string associated with the error return status
      - htonl()
        Convert a 32-bit value from host-byte order to network-byte order
      - htons()
        Convert a 16-bit value from host-byte order to network-byte order
      - hwi_find()
        Find a specific item instance owned by a specific parent, resolving all synonym names
      - hwi_find_bus()
        Find the offset of the section in the system page for a bus
      - hwi_find_compatible()
        Find a specific instance of an device by its compatible string
      - hwi_find_device()
        Find the offset in the system page of a device
      - hwi_find_devicebus()
        Find the bus that a device belongs to
      - hwi_find_item()
        Find an item in the hwinfo structure
      - hwi_find_num_units()
        Count the instances of a unit in the system page
      - hwi_find_tag()
        Find a tag in the hwinfo structure
      - hwi_find_unit()
        Determine which instance of a device an offset corresponds to
      - hwi_next_item()
        Find the next item in the hwinfo structure
      - hwi_next_tag()
        Find the next tag in the hwinfo structure
      - hwi_off2tag()
        Return a pointer to the start of a tag in the hwinfo area of the system page
      - hwi_tag2off()
        Return the offset from the start of the hwinfo area of the system page
      - hwi_tag_find()
        Locate a specific instance of the named tag for a device
      - hwiattr_get(), hwiattr_get_*()
        Get attributes of a bus or device
      - hwitag_find_busattr()
        Find a bus attribute tag associated with a bus
      - hwitag_find_clkfreq()
        Find the clock source for a device
      - hwitag_find_errata()
        Find an erratum for a device
      - hwitag_find_ivec()
        Find the interrupt vector associated with a device
      - hwitag_find_nicaddr()
        Get the NIC address of a device
      - hwitag_find_phyaddr()
        Find the PHY address associated with a device
      - hypot(), hypotf(), hypotl()
        Calculate the length of the hypotenuse for a right-angled triangle
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    - Full Safety Information
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  - Devctl and Ioctl Commands
  - JSON Library Reference
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  - 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.
QNX Hypervisor
The QNX Hypervisor allows you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX software in Amazon Web Services (AWS) and Microsoft Azure (Azure).
QNX Advanced Virtualization Frameworks User's Guide
This User's Guide is aimed at all systems integrators and developers who want to design and build embedded systems using the QNX Advanced Virtualization Frameworks.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation and explains how to obtain technical support.

`h_errno`

Host error variable

Synopsis:

#include <netdb.h>

extern int h_errno;

Library:

libsocket

Use the -l socket option to qcc to link against this library.

Description:

The h_errno variable can be set by any one of the following functions:

It can be set to any one of the following:

HOST_NOT_FOUND: Authoritative answer: Unknown host.
NETDB_INTERNAL: You specified an invalid address family when calling gethostbyname2().
NO_DATA: Valid name, no data record of the requested type. The name is known to the name server, but has no IP address associated with it—this isn't a temporary error. Another type of request to the name server using this domain name will result in an answer (e.g. a mail-forwarder may be registered for this domain).
NO_RECOVERY: Unknown server error. An unexpected server failure was encountered. This is a nonrecoverable network error.
TRY_AGAIN: Nonauthoritative answer: Host name lookup failure. This is usually a temporary error and means that the local server didn't receive a response from an authoritative server. A retry at some later time may succeed.

Classification:

Standard Unix; removed from POSIX.1-2008

Page updated: March 12, 2026