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explain_writev(3)	   Library Functions Manual	     explain_writev(3)

NAME
       explain_writev -	explain	writev(2) errors

SYNOPSIS
       #include	<libexplain/writev.h>
       const char *explain_writev(int fildes, const struct iovec *data,	int
       data_size);
       const char *explain_errno_writev(int errnum, int	fildes,	const struct
       iovec *data, int	data_size);
       void explain_message_writev(char	*message, int message_size, int
       fildes, const struct iovec *data, int data_size);
       void explain_message_errno_writev(char *message,	int message_size, int
       errnum, int fildes, const struct	iovec *data, int data_size);

DESCRIPTION
       These  functions	may be used to obtain explanations for errors returned
       by the writev(2)	system call.

   explain_writev
       const char *explain_writev(int fildes, const struct iovec *data,	int
       data_size);

       The  explain_writev function is used to obtain an explanation of	an er-
       ror returned by the writev(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 errno global	variable will be used to obtain	the error value	to  be
       decoded.

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

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

       data_size
	       The original data_size, exactly as passed to the	writev(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, 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:
	      ssize_t result = writev(fildes, data, data_size);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_writev(fildes, data,
		  data_size));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_writev
       const char *explain_errno_writev(int errnum, int	fildes,	const struct
       iovec *data, int	data_size);

       The  explain_errno_writev  function is used to obtain an	explanation of
       an error	returned by the	writev(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.

       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.

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

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

       data_size
	       The original data_size, exactly as passed to the	writev(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,  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:
	      ssize_t result = writev(fildes, data, data_size);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_writev(err, fildes,
		  data,	data_size));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_writev
       void explain_message_writev(char	*message, int message_size, int
       fildes, const struct iovec *data, int data_size);

       The explain_message_writev function is used to obtain an	explanation of
       an  error  returned by the writev(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  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.

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

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

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

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      ssize_t result = writev(fildes, data, data_size);
	      if (result < 0)
	      {
		  char message[3000];
		  explain_message_writev(message, sizeof(message), fildes,
		  data,	data_size);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_errno_writev
       void explain_message_errno_writev(char *message,	int message_size, int
       errnum, int fildes, const struct	iovec *data, int data_size);

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

       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.

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

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

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

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

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

SEE ALSO
       writev(2)
	       write data from multiple	buffers

       explain_writev_or_die(3)
	       write data from multiple	buffers	and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2009 Peter	Miller

							     explain_writev(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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