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explain_write(3)	   Library Functions Manual	      explain_write(3)

NAME
       explain_write - explain write(2)	errors

SYNOPSIS
       #include	<libexplain/write.h>
       const   char   *explain_write(int   fildes,   const  void  *data,  long
       data_size);
       const char *explain_errno_write(int  errnum,  int  fildes,  const  void
       *data, long data_size);
       void explain_message_write(char *message, int message_size, int fildes,
       const void *data, long data_size);
       void explain_message_errno_write(char *message, int  message_size,  int
       errnum, int fildes, const void *data, long data_size);

DESCRIPTION
       These  functions	may be used to obtain explanations for write(2)	errors
       .

   explain_write
       const  char  *explain_write(int	fildes,	  const	  void	 *data,	  long
       data_size);

       The  explain_write  function may	be used	to obtain a human readable ex-
       planation of what went wrong in a write(2) 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 error number	will be	picked up from the errno global	variable.

       This function is	intended to be used in a fashion similar to  the  fol-
       lowing example:
	      sszie_t n	= write(fd, data, data_size);
	      if (n < 0)
	      {
		  fprintf(stderr, '%s0,	explain_read(fd, data, data_size));
		  exit(EXIT_FAILURE);
	      }

       fildes  The  original  fildes, exactly as passed	to the write(2)	system
	       call.

       data    The original data, exactly as passed  to	 the  write(2)	system
	       call.

       data_size
	       The  original data_size,	exactly	as passed to the write(2) sys-
	       tem 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_write
       const  char  *explain_errno_write(int  errnum,  int  fildes, const void
       *data, long data_size);

       The explain_errno_write function	may be used to obtain a	human readable
       explanation  of	what  went wrong in a write(2) 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:
	      sszie_t n	= write(fd, data, data_size);
	      if (n < 0)
	      {
		  int err = errno;
		  fprintf(stderr, '%s0,	explain_errno_read(errnum, fd, data,
		      data_size));
		  exit(EXIT_FAILURE);
	      }

       errnum  The  error  value  to be	decoded, usually obtain	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.

       fildes  The  orginal  fildes,  exactly as passed	to the write(2)	system
	       call.

       data    The original data, exactly as passed  to	 the  write(2)	system
	       call.

       data_size
	       The  original data_size,	exactly	as passed to the write(2) sys-
	       tem 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_write
       void explain_message_write(char *message, int message_size, int fildes,
       const void *data, long data_size);

       The explain_message_write function may be used to obtain	a human	 read-
       able  explanation  of  what  went wrong in a write(2) 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 error number	will be	picked up from the errno global	variable.

       This function is	intended to be used in a fashion similar to  the  fol-
       lowing example:
	      sszie_t n	= write(fd, data, data_size);
	      if (n < 0)
	      {
		  char message[3000];
		  explain_message_read(message,	sizeof(message), fd, data,
		      data_size));
		  fprintf(stderr, '%s0,	message);
		  exit(EXIT_FAILURE);
	      }

       message The location in which to	store the returned message.  Because a
	       message return buffer  has  been	 supplied,  this  function  is
	       thread safe.

       message_size
	       The  size  in  bytes  of	the location in	which to store the re-
	       turned message.

       fildes  The original fildes, exactly as passed to the  write(2)	system
	       call.

       data    The  original  data,  exactly  as passed	to the write(2)	system
	       call.

       data_size
	       The original data_size, exactly as passed to the	write(2)  sys-
	       tem call.

       Note:  Given  a	suitably  thread  safe buffer, this function is	thread
       safe.

   explain_message_errno_write
       void explain_message_errno_write(char * message,	int message_size,  int
       errnum, int fildes, const void *data, long data_size);

       The  explain_message_errno_write	function may be	used to	obtain a human
       readable	explanation of what went wrong in a write(2) 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:
	      sszie_t n	= write(fd, data, data_size);
	      if (n < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_read(message, sizeof(message), errno,
		      fd, data,	data_size));
		  fprintf(stderr, '%s0,	message);
		  exit(EXIT_FAILURE);
	      }

       message The location in which to	store the returned message.  Because a
	       message	return	buffer	has  been  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 obtain	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.

       fildes  The  original  fildes, exactly as passed	to the write(2)	system
	       call.

       data    The original data, exactly as passed  to	 the  write(2)	system
	       call.

       data_size
	       The  original data_size,	exactly	as passed to the write(2) sys-
	       tem call.

       Note: Given a suitably thread safe  buffer,  this  function  is	thread
       safe.

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

AUTHOR
       Written by Peter	Miller <pmiller@opensource.org.au>

							      explain_write(3)

NAME | SYNOPSIS | DESCRIPTION | COPYRIGHT | AUTHOR

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