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explain_printf(3)	   Library Functions Manual	     explain_printf(3)

NAME
       explain_printf -	explain	printf(3) errors

SYNOPSIS
       #include	<libexplain/printf.h>
       const char *explain_printf(const	char *format);
       const char *explain_errno_printf(int errnum, const char *format);
       void explain_message_printf(char	*message, int message_size, const char
       *format);
       void explain_message_errno_printf(char *message,	int message_size, int
       errnum, const char *format);

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

   explain_printf
       const char *explain_printf(const	char *format);

       The explain_printf function is used to obtain an	explanation of an  er-
       ror  returned  by the printf(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.

       format  The original format, exactly as passed to the printf(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 = 0;
	      int result = printf(format);
	      if (result < 0 &&	errno != 0)
	      {
		  fprintf(stderr, "%s\n", explain_printf(format));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_printf
       const char *explain_errno_printf(int errnum, const char *format);

       The explain_errno_printf	function is used to obtain an  explanation  of
       an  error  returned by the printf(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.

       format  The  original format, exactly as	passed to the printf(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 = 0;
	      int result = printf(format);
	      if (result < 0 &&	errno != 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_printf(err, format));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_printf
       void explain_message_printf(char	*message, int message_size, const char
       *format);

       The explain_message_printf function is used to obtain an	explanation of
       an  error  returned by the printf(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.

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

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

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

   explain_message_errno_printf
       void explain_message_errno_printf(char *message,	int message_size, int
       errnum, const char *format);

       The explain_message_errno_printf	function is used to obtain an explana-
       tion of an error	returned by the	printf(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.

       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.

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

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

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

SEE ALSO
       printf(3)
	       formatted output	conversion

       explain_printf_or_die(3)
	       formatted output	conversion and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							     explain_printf(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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