explain_fread(3)					     Library Functions Manual						  explain_fread(3)

NAME

       explain_fread - explain fread(3) errors

SYNOPSIS

       #include <libexplain/fread.h>
       const char *explain_fread(void *ptr, size_t size, size_t nmemb, FILE *fp);
       const char *explain_errno_fread(int errnum, void *ptr, size_t size, size_t nmemb, FILE *fp);
       void explain_message_fread(char *message, int message_size, void *ptr, size_t size, size_t nmemb, FILE *fp);
       void explain_message_errno_fread(char *message, int message_size, int errnum, void *ptr, size_t size, size_t nmemb, FILE *fp);

DESCRIPTION

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

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

       The  explain_fread  function is used to obtain an explanation of an error returned by the fread(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:
	      size_t how_many = fread(ptr, size, nmemb, fp);
	      if (how_many == 0 && ferror(fp))
	      {
		  fprintf(stderr, "%s
", explain_fread(ptr, size, nmemb, fp));
		  exit(EXIT_FAILURE);
	      }

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

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

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

       fp      The original fp, exactly as passed to the fread(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_fread
       const char *explain_errno_fread(int errnum, void *ptr, size_t size, size_t nmemb, FILE *fp);

       The explain_errno_fread function is used to obtain an explanation of an error returned by the fread(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:
	      size_t how_many = fread(ptr, size, nmemb, fp);
	      if (how_many == 0 && ferror(fp))
	      {
		  int err = errno;
		  fprintf(stderr, "%s
", explain_errno_fread(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 neces-
	       sary 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 fread(3) system call.

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

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

       fp      The original fp, exactly as passed to the fread(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_fread
       void explain_message_fread(char *message, int message_size, void *ptr, size_t size, size_t nmemb, FILE *fp);

       The  explain_message_fread  function may be used to  obtain an explanation of an error returned by the fread(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:
	      size_t how_many = fread(ptr, size, nmemb, fp);
	      if (how_many == 0 && ferror(fp))
	      {
		  char message[3000];
		  explain_message_fread(message, sizeof(message), ptr, size, nmemb, fp);
		  fprintf(stderr, "%s
", 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 fread(3) system call.

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

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

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

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

       The  explain_message_errno_fread function may be used to obtain an explanation of an error returned by the fread(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:
	      size_t how_many = fread(ptr, size, nmemb, fp);
	      if (how_many == 0 && ferror(fp))
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_fread(message, sizeof(message), err,
		      ptr, size, nmemb, fp);
		  fprintf(stderr, "%s
", 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 neces-
	       sary 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 fread(3) system call.

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

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

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

SEE ALSO

       fread(3)
	       binary stream input

       explain_fread_or_die(3)
	       binary stream input and report errors

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2008 Peter Miller

																  explain_fread(3)