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 0.19
Copyright (C) 2008 Peter Miller
explain_fwrite(3)