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explain_ustat(3)	   Library Functions Manual	      explain_ustat(3)

NAME
       explain_ustat - explain ustat(2)	errors

SYNOPSIS
       #include	<libexplain/ustat.h>
       const char *explain_ustat(dev_t dev, struct ustat *ubuf);
       const char *explain_errno_ustat(int errnum, dev_t dev, struct ustat
       *ubuf);
       void explain_message_ustat(char *message, int message_size, dev_t dev,
       struct ustat *ubuf);
       void explain_message_errno_ustat(char *message, int message_size, int
       errnum, dev_t dev, struct ustat *ubuf);

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

   explain_ustat
       const char *explain_ustat(dev_t dev, struct ustat *ubuf);

       The explain_ustat function is used to obtain an explanation of an error
       returned	by the ustat(2)	system call. The least the message  will  con-
       tain  is	the value of strerror(errno), but usually it will do much bet-
       ter, and	indicate the underlying	cause in more detail.

       The errno global	variable will be used to obtain	the error value	to  be
       decoded.

       dev     The  original  dev,  exactly  as	 passed	to the ustat(2)	system
	       call.

       ubuf    The original ubuf, exactly as passed  to	 the  ustat(2)	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:
	      if (ustat(dev, ubuf) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_ustat(dev, ubuf));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_ustat
       const char *explain_errno_ustat(int errnum, dev_t dev, struct ustat
       *ubuf);

       The explain_errno_ustat function	is used	to obtain an explanation of an
       error returned by the ustat(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.

       dev     The original dev, exactly as  passed  to	 the  ustat(2)	system
	       call.

       ubuf    The  original  ubuf,  exactly  as passed	to the ustat(2)	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:
	      if (ustat(dev, ubuf) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_ustat(err, dev,
		  ubuf));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_ustat
       void explain_message_ustat(char *message, int message_size, dev_t dev,
       struct ustat *ubuf);

       The  explain_message_ustat function is used to obtain an	explanation of
       an error	returned by the	ustat(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.

       dev     The original dev, exactly as  passed  to	 the  ustat(2)	system
	       call.

       ubuf    The  original  ubuf,  exactly  as passed	to the ustat(2)	system
	       call.

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      if (ustat(dev, ubuf) < 0)
	      {
		  char message[3000];
		  explain_message_ustat(message, sizeof(message), dev, ubuf);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_errno_ustat
       void explain_message_errno_ustat(char *message, int message_size, int
       errnum, dev_t dev, struct ustat *ubuf);

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

       dev     The  original  dev,  exactly  as	 passed	to the ustat(2)	system
	       call.

       ubuf    The original ubuf, exactly as passed  to	 the  ustat(2)	system
	       call.

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

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

SEE ALSO
       ustat(2)
	       get file	system statistics

       explain_ustat_or_die(3)
	       get file	system statistics and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2009 Peter	Miller

							      explain_ustat(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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