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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
Devctl and Ioctl Commands
FIO*
FIONREAD
Determine the number of characters waiting to be read

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.
- OS Components & Operations
- Graphics
- Programming
- 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
  - Devctl and Ioctl Commands
    - BIOC*
    - CAN_DEVCTL_*
    - DCMD_ALL_*
    - DCMD_BLK_*
    - DCMD_CAM_*
    - DCMD_CHR_*
    - DCMD_DUMPER_*
    - DCMD_F3S_*
    - DCMD_FSYS_*
    - DCMD_IP_*
    - DCMD_MEMMGR_*
    - DCMD_MISC_*
    - DCMD_MMCSD_*
    - DCMD_PROC_*
    - DCMD_PROF_*
    - DCMD_PTPD_*
    - DCMD_SDIO_*
    - DCMD_SDMMC_*
    - DCMD_SPI_*
    - PTP_*
    - FIO*
      - FIOASYNC
        Set or clear asynchronous I/O
      - FIOCLEX
        Set close on exec on a file descriptor
      - FIOGETOWN
        Get the owner of a file
      - FIONBIO
        Set or clear nonblocking I/O
      - FIONCLEX
        Clear close on exec on a file descriptor
      - FIONREAD
        Determine the number of characters waiting to be read
      - FIONSPACE
        Get the amount of space in the send queue
      - FIONWRITE
        Get the number of bytes outstanding in the send queue.
      - FIOSETOWN
        Set the owner of a file
    - TC*
    - TIOC*
  - 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.

FIONREAD

QNX SDP8.0Devctl and Ioctl CommandsDeveloper

Determine the number of characters waiting to be read

Synopsis:

#include <sys/ioctl.h>

#define FIONREAD        _IOR('f', 127, int)

Arguments to ioctl():


Argument	Value
`fd`	A file descriptor that you obtained by opening the device
`request`	FIONREAD
Additional argument	A pointer to an int

Description:

This command determine the number of characters waiting to be read. It's also implemented as the DCMD_CHR_ISCHARS devctl() command.

Note:

This command is for internal use, and you shouldn't use it directly. Instead use the tcischars() cover function.

Input:

None.

Output:

The number of characters.