man explain_fwrite (3): 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.

SYNOPSIS

DESCRIPTION

explain_fwrite

explain_errno_fwrite

explain_message_fwrite

explain_message_errno_fwrite

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