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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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T
tcischars()
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.
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        Get the process group ID of the session leader for a controlling terminal
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        Get the size of a character device
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        Determine the number of characters waiting to be read
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        Assert a break condition over a communications line
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        Terminal control structure
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        Compute the gamma function of a number
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        Destroy a process timer
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        Get information about a timer
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        Arm a timer with the given expiration time, disarm it, or set its tolerance
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        Get time-accounting information
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        Time-specification structure
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        Get the number of seconds and nanoseconds since a given epoch
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        Convert a timespec structure to nanoseconds
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        The number of seconds by which the local time zone is earlier than UTC
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        Structure that describes calendar time
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        Create a temporary file
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        Generate a unique string for use as a filename
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        Convert a character to lowercase
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        Convert a wide character in a specified manner
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        Convert a wide character to lowercase
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        Convert a wide character to uppercase
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        Insert a trace event for the entry to a function
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        Insert a trace event for the exit from a function
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        Get the flag from the header of a trace event
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        Insert a trace event for the current address
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        Insert a user combine trace event
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        Insert a trace event of an arbitrary class and type with arbitrary data
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        Insert a user string trace event
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        Insert a user simple trace event
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        Insert a user string trace event, specifying a maximum string length
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        Insert a user string trace event, using a variable argument list
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        Control the tracing of kernel events
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        Process trace data
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        Attach a callback to a trace event
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        Attach a callback to a range of events
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        Set the traceparser debug modes
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        Destroy a traceparser state structure
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        Get information about traceparser
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        Initialize the traceparser state information
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        Round to a truncated integer value
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        Delete thread-specific storage
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        Set a thread-specific data value
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        Get a fully qualified pathname for a file
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        Get a fully qualified pathname for a file
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        The abbreviations for the time zone for standard and daylight savings time
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        Set the time according to the current time zone
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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.

tcischars()

QNX SDP8.0C Library ReferenceAPIDeveloper

Determine the number of characters waiting to be read

Synopsis:

#include <termios.h>

int tcischars( int filedes );

Arguments:

filedes: A file descriptor that's associated with the device that you want to check.

Library:

libc

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

Description:

The tcischars() function checks to see how many characters are waiting to be read from the given file descriptor, filedes.

Returns:

The number of characters waiting to be read, or -1 if an error occurred.

Errors:

ENOTTY: The filedes argument isn't the file descriptor for a character device.

Classification:

QNX OS


Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Page updated: August 11, 2025