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explain_vfprintf(3)	   Library Functions Manual	   explain_vfprintf(3)

NAME
       explain_vfprintf	- explain vfprintf(3) errors

SYNOPSIS
       #include	<libexplain/vfprintf.h>
       const char *explain_vfprintf(FILE *fp, const char *format, va_list ap);
       const char *explain_errno_vfprintf(int errnum, FILE *fp,	const char
       *format,	va_list	ap);
       void explain_message_vfprintf(char *message, int	message_size, FILE
       *fp, const char *format,	va_list	ap);
       void explain_message_errno_vfprintf(char	*message, int message_size,
       int errnum, FILE	*fp, const char	*format, va_list ap);

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

   explain_vfprintf
       const char *explain_vfprintf(FILE *fp, const char *format, va_list ap);

       The  explain_vfprintf  function	is used	to obtain an explanation of an
       error returned by the vfprintf(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.

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

       format  The original format, exactly as passed to the vfprintf(3)  sys-
	       tem call.

       ap      The  original  ap,  exactly as passed to	the vfprintf(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 buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_vfprintf(fp, format, ap));
		  exit(EXIT_FAILURE);
	      }

       The above code example is available  pre-packaged  as  the  explain_vf-
       printf_or_die(3)	function.

   explain_errno_vfprintf
       const char *explain_errno_vfprintf(int errnum, FILE *fp,	const char
       *format,	va_list	ap);

       The explain_errno_vfprintf function is used to obtain an	explanation of
       an  error  returned by the vfprintf(3) system call.  The	least the mes-
       sage will contain is the	value of strerror(errno), but usually it  will
       do much better, and indicate the	underlying cause in more detail.

       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 vfprintf(3)	system
	       call.

       format  The original format, exactly as passed to the vfprintf(3)  sys-
	       tem call.

       ap      The  original  ap,  exactly as passed to	the vfprintf(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 buf-
       fer across all threads, and many	other functions	in this	library.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_vfprintf(err, fp, for-
		  mat, ap));
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is available pre-packaged as the explain_vf-
       printf_or_die(3)	function.

   explain_message_vfprintf
       void explain_message_vfprintf(char *message, int	message_size, FILE
       *fp, const char *format,	va_list	ap);

       The  explain_message_vfprintf function is used to obtain	an explanation
       of an error returned by the vfprintf(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.

       message The location in which to	store the returned message. If a suit-
	       able 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  vfprintf(3)	system
	       call.

       format  The  original format, exactly as	passed to the vfprintf(3) sys-
	       tem call.

       ap      The original ap,	exactly	as passed to  the  vfprintf(3)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
	      {
		  char message[3000];
		  explain_message_vfprintf(message, sizeof(message), fp, for-
		  mat, ap);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is available pre-packaged as the explain_vf-
       printf_or_die(3)	function.

   explain_message_errno_vfprintf
       void explain_message_errno_vfprintf(char	*message, int message_size,
       int errnum, FILE	*fp, const char	*format, va_list ap);

       The explain_message_errno_vfprintf function is used to obtain an	expla-
       nation of an error returned by the vfprintf(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  de-
       tail.

       message The location in which to	store the returned message. If a suit-
	       able 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  vfprintf(3)	system
	       call.

       format  The  original format, exactly as	passed to the vfprintf(3) sys-
	       tem call.

       ap      The original ap,	exactly	as passed to  the  vfprintf(3)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      errno = EINVAL; if (vfprintf(fp, format, ap) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_vfprintf(message, sizeof(message),
		  err, fp, format, ap);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The  above  code	 example  is available pre-packaged as the explain_vf-
       printf_or_die(3)	function.

SEE ALSO
       vfprintf(3)
	       formatted output	conversion

       explain_vfprintf_or_die(3)
	       formatted output	conversion and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							   explain_vfprintf(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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