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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  con-
       tain  is	the value of strerror(errno), but usually it will do much bet-
       ter, 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 fol-
       lowing example:
	      size_t how_many =	fread(ptr, size, nmemb,	fp);
	      if (how_many == 0	&& ferror(fp))
	      {
		  fprintf(stderr, "%s\n", 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,  in-
	       cluding other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer 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  fol-
       lowing example:
	      size_t how_many =	fread(ptr, size, nmemb,	fp);
	      if (how_many == 0	&& ferror(fp))
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", 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
	       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 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, in-
	       cluding other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer 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  explana-
       tion  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  fol-
       lowing 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\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 re-
	       turned 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  ex-
       planation  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 de-
       tail.

       This function is	intended to be used in a fashion similar to  the  fol-
       lowing 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\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 re-
	       turned 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  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 1.3
       Copyright (C) 2008 Peter	Miller

							      explain_fread(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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