explain_fwrite(3)

NAME
explain_fwrite - explain fwrite(3) errors

SYNOPSIS
#include <libexplain/fwrite.h>

const char *explain_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *fp);
const char *explain_errno_fwrite(int errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);
void explain_message_fwrite(char *message, int message_size, const void *ptr, size_t size, size_t nmemb, FILE *fp);
void explain_message_errno_fwrite(char *message, int message_size, int errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);

DESCRIPTION
These functions may be used to obtain explanations for errors returned by the fwrite(3) system call.

  explain_fwrite
const char *explain_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *fp);

The explain_fwrite function is used to obtain an explanation of an error returned by the fwrite(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:
    if (fwrite(ptr, size, nmemb, fp) < 0)
    {
        fprintf(stderr, "%s\n", explain_fwrite(ptr, size, nmemb, fp));
        exit(EXIT_FAILURE);
    }

ptr The original ptr, exactly as passed to the fwrite(3) system call.

size
    The original size, exactly as passed to the fwrite(3) system call.

nmemb
    The original nmemb, exactly as passed to the fwrite(3) system call.

fp  The original fp, exactly as passed to the fwrite(3) 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.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

  explain_errno_fwrite
const char *explain_errno_fwrite(int errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);

The explain_errno_fwrite function is used to obtain an explanation of an error returned by the fwrite(3) system call. The least the message will contain is the value of 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:
    if (fwrite(ptr, size, nmemb, fp) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fwrite(err,
            ptr, size, nmemb, fp));
        exit(EXIT_FAILURE);
    }

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

ptr The original ptr, exactly as passed to the fwrite(3) system call.

size
    The original size, exactly as passed to the fwrite(3) system call.

nmemb
    The original nmemb, exactly as passed to the fwrite(3) system call.

fp  The original fp, exactly as passed to the fwrite(3) 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.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

  explain_message_fwrite
void explain_message_fwrite(char *message, int message_size, const void *ptr, size_t size, size_t nmemb, FILE *fp);

The explain_message_fwrite function may be used to obtain an explanation of an error returned by the fwrite(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:
    if (fwrite(ptr, size, nmemb, fp) < 0)
    {
        char message[3000];
        explain_message_fwrite(message, sizeof(message), ptr, size, nmemb, fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

ptr The original ptr, exactly as passed to the fwrite(3) system call.

size
    The original size, exactly as passed to the fwrite(3) system call.

nmemb
    The original nmemb, exactly as passed to the fwrite(3) system call.

fp  The original fp, exactly as passed to the fwrite(3) system call.

  explain_message_errno_fwrite
void explain_message_errno_fwrite(char *message, int message_size, int errnum, const void *ptr, size_t size, size_t nmemb, FILE *fp);

The explain_message_errno_fwrite function may be used to obtain an explanation of an error returned by the fwrite(3) system call. The least the message will contain is the value of 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:
    if (fwrite(ptr, size, nmemb, fp) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_fwrite(message, sizeof(message), err,
            ptr, size, nmemb, fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

ptr The original ptr, exactly as passed to the fwrite(3) system call.

size
    The original size, exactly as passed to the fwrite(3) system call.

nmemb
    The original nmemb, exactly as passed to the fwrite(3) system call.

fp  The original fp, exactly as passed to the fwrite(3) system call.

SEE ALSO

fwrite(3)
    binary stream output

explain_fwrite_or_die(3)
    binary stream output and report errors

COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller