GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages


Manual Reference Pages  -  EXPLAIN_READ (3)

NAME

explain_read - explain read(2) errors

CONTENTS

Synopsis
Description
Copyright
Author

SYNOPSIS

#include <libexplain/read.h>
const char *explain_read(int fildes, const void *data, long data_size);
const char *explain_errno_read(int errnum, int fildes, const void *data, long data_size);
void explain_message_read(char *message, int message_size, int fildes, const void *data, long data_size);
void explain_message_errno_read(char *message, int message_size, int errnum, int fildes, const void *data, long data_size);

DESCRIPTION

These functions may be used to obtain an explanation for I]read(2) errors.

    explain_read

const char *explain_read(int fildes, const void *data, long data_size);

The explain_read function may be used to obtain a human readable explanation of what went wrong in a I]read(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The error number will be picked up from the I]errno global variable.

This function is intended to be used in a fashion similar to the following example:

ssize_t n = read(fd, data, data_size);
if (n < 0)
{
    fprintf(stderr, "%s\n", explain_read(fd, data, data_size));
    exit(EXIT_FAILURE);
}

I]fildes The original fildes, exactly as passed to the I]read(2) system call.
I]data The original data, exactly as passed to the I]read(2) system call.
I]data_size
  The original data_size, exactly as passed to the I]read(2) system call.
Returns: The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
B]Note: This function is B]not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

    explain_errno_read

const char *explain_errno_read(int errnum, int fildes, const void *data, long data_size);

The explain_errno_read function may be used to obtain a human readable explanation of what went wrong in a I]read(2) system call. The least the message will contain is the value of CW]strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:

ssize_t n = read(fd, data, data_size);
if (n < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_read(err, fd, data, data_size));
    exit(EXIT_FAILURE);
}

I]errnum The error value to be decoded, usually obtain from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]fildes The original fildes, exactly as passed to the I]read(2) system call.
I]data The original data, exactly as passed to the I]read(2) system call.
I]data_size
  The original data_size, exactly as passed to the I]read(2) system call.
Returns: The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
B]Note: This function is B]not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

    explain_message_read

void explain_message_read(char *message, int message_size, int fildes, const void *data, long data_size);

The explain_message_read function may be used to obtain a human readable explanation of what went wrong in a I]read(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The error number will be picked up from the I]errno global variable.

This function is intended to be used in a fashion similar to the following example:

ssize_t n = read(fd, data, data_size);
if (n < 0)
{
    char message[3000];
    explain_message_read(message, sizeof(message), fd, data, data_size));
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

I]message
  The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]fildes The original fildes, exactly as passed to the I]read(2) system call.
I]data The original data, exactly as passed to the I]read(2) system call.
I]data_size
  The original data_size, exactly as passed to the I]read(2) system call.
B]Note: Given a suitably thread safe buffer, this function is thread safe.

    explain_message_errno_read

void explain_message_errno_read(char *message, int message_size, int errnum, int fildes, const void *data, long data_size);

The explain_message_errno_read function may be used to obtain a human readable explanation of what went wrong in a I]read(2) system call. The least the message will contain is the value of CW]strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:

ssize_t n = read(fd, data, data_size);
if (n < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_read(message, sizeof(message), err,
        fd, data, data_size);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

I]message
  The location in which to store the returned message. Because a message return buffer has been supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]errnum The error value to be decoded, usually obtain from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]fildes The original fildes, exactly as passed to the I]read(2) system call.
I]data The original data, exactly as passed to the I]read(2) system call.
I]data_size
  The original data_size, exactly as passed to the I]read(2) system call.
B]Note: Given a suitably thread safe buffer, this function is thread safe.

COPYRIGHT

libexplain version 1.3
Copyright © 2008 Peter Miller

AUTHOR

Written by Peter Miller <pmiller@opensource.org.au>
Search for    or go to Top of page |  Section 3 |  Main Index


EXPLAIN_READ (3) -->

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.