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AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 1

fubyte Kernel Service


Retrieves a byte of data from user memory.


#include <sys/types.h>
#include <sys/errno.h>

int fubyte ( uaddr)
uchar *uaddr;


uaddr Specifies the address of the user data.


The fubyte kernel service fetches, or retrieves, a byte of data from the specified address in user memory. It is provided so that system calls and device heads can safely access user data. The fubyte service ensures that the user has the appropriate authority to:

The fubyte service should be called only while executing in kernel mode in the user process.

Execution Environment

The fubyte kernel service can be called from the process environment only.

Return Values

When successful, the fubyte service returns the specified byte.

-1 Indicates a uaddr parameter that is not valid.

The access is not valid under the following circumstances:

Implementation Specifics

The fubyte kernel service is part of Base Operating System (BOS) Runtime.

Related Information

The fuword kernel service, subyte kernel service, suword kernel service.

Accessing User-Mode Data while in Kernel Mode and Memory Kernel Services in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.

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