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 1.4
       Copyright (C) 2008 Peter Miller

                                                                                               explain_fwrite(3)