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explain_fprintf(3)	   Library Functions Manual	    explain_fprintf(3)

NAME
       explain_fprintf - explain fprintf(3) errors

SYNOPSIS
       #include	<libexplain/fprintf.h>
       const char *explain_fprintf(FILE	*fp, const char	*format, ...);
       const char *explain_errno_fprintf(int errnum, FILE *fp, const char
       *format,	...);
       void explain_message_fprintf(char *message, int message_size, FILE *fp,
       const char *format, ....);
       void explain_message_errno_fprintf(char *message, int message_size, int
       errnum, FILE *fp, const char *format, ...);

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

   explain_fprintf
       const char *explain_fprintf(FILE	*fp, const char	*format, ...);

       The explain_fprintf function is used to obtain an explanation of	an er-
       ror returned by the fprintf(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 fprintf(3)	system
	       call.

       format  The original format, exactly as passed to the fprintf(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;
	      int result = fprintf(fp, format, ...);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_fprintf(fp, format, ...));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_fprintf
       const char *explain_errno_fprintf(int errnum, FILE *fp, const char
       *format,	...);

       The  explain_errno_fprintf function is used to obtain an	explanation of
       an error	returned by the	fprintf(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.

       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  fprintf(3)	system
	       call.

       format  The original format, exactly as passed to the fprintf(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;
	      int result = fprintf(fp, format, ...);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_fprintf(err, fp, for-
		  mat, ...));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_fprintf
       void explain_message_fprintf(char *message, int message_size, FILE *fp,
       const char *format, ...);

       The  explain_message_fprintf  function is used to obtain	an explanation
       of an error returned by the fprintf(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.

       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  fprintf(3)	system
	       call.

       format  The original format, exactly as passed to the fprintf(3)	system
	       call.

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

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

   explain_message_errno_fprintf
       void explain_message_errno_fprintf(char *message, int message_size, int
       errnum, FILE *fp, const char *format, ...);

       The explain_message_errno_fprintf function is used to obtain an	expla-
       nation  of  an  error returned by the fprintf(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 fprintf(3)	system
	       call.

       format  The original format, exactly as passed to the fprintf(3)	system
	       call.

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

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

SEE ALSO
       fprintf(3)
	       formatted output	conversion

       explain_fprintf_or_die(3)
	       formatted output	conversion and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							    explain_fprintf(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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