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explain_ferror(3)	   Library Functions Manual	     explain_ferror(3)

NAME
       explain_ferror -	explain	ferror(3) errors

SYNOPSIS
       #include	<libexplain/ferror.h>
       const char *explain_ferror(FILE *fp);
       const char *explain_errno_ferror(int errnum, FILE *fp);
       void explain_message_ferror(char	*message, int message_size, FILE *fp);
       void  explain_message_errno_ferror(char *message, int message_size, int
       errnum, FILE *fp);

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

   explain_ferror
       const char *explain_ferror(FILE *fp);

       The  explain_ferror function is used to obtain an explanation of	an er-
       ror returned by the ferror(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:
	      if (ferror(fp) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_ferror(fp));
		  exit(EXIT_FAILURE);
	      }

       It is essential that this function cal be placed	as close  as  possible
       to the I/O code that has	caused the problem, otherwise intervening code
       could have altered the errno global variable.

       fp      The original fp,	exactly	as  passed  to	the  ferror(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_ferror
       const char *explain_errno_ferror(int errnum, FILE *fp);

       The explain_errno_ferror	function is used to obtain an  explanation  of
       an  error returned by the ferror(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:
	      if (ferror(fp) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_ferror(err, fp));
		  exit(EXIT_FAILURE);
	      }

       It is essential that this function cal be placed	as close  as  possible
       to the I/O code that has	caused the problem, otherwise intervening code
       could have altered the errno global variable.

       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.

       fp      The original fp,	exactly	as  passed  to	the  ferror(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_ferror
       void explain_message_ferror(char	*message, int message_size, FILE *fp);

       The explain_message_ferror function may be used to  obtain an  explana-
       tion  of	an error returned by the ferror(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:
	      if (ferror(fp) < 0)
	      {
		  char message[3000];
		  explain_message_ferror(message, sizeof(message), fp);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       It  is  essential that this function cal	be placed as close as possible
       to the I/O code that has	caused the problem, otherwise intervening code
       could have altered the errno global variable.

       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.

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

   explain_message_errno_ferror
       void  explain_message_errno_ferror(char *message, int message_size, int
       errnum, FILE *fp);

       The explain_message_errno_ferror	function may be	used to	obtain an  ex-
       planation of an error returned by the ferror(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:
	      if (ferror(fp) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_ferror(message,	sizeof(message), err, fp);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       It  is  essential that this function cal	be placed as close as possible
       to the I/O code that has	caused the problem, otherwise intervening code
       could have altered the errno global variable.

       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.

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

SEE ALSO
       ferror(3)
	       check stream status

       explain_ferror_or_die(3)
	       check stream status and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							     explain_ferror(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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