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explain_openat(3)	   Library Functions Manual	     explain_openat(3)

NAME
       explain_openat -	explain	openat(2) errors

SYNOPSIS
       #include	<libexplain/openat.h>
       const char *explain_openat(int fildes, const char *pathname, int	flags,
       mode_t mode);
       const char *explain_errno_openat(int errnum, int	fildes,	const char
       *pathname, int flags, mode_t mode);
       void explain_message_openat(char	*message, int message_size, int
       fildes, const char *pathname, int flags,	mode_t mode);
       void explain_message_errno_openat(char *message,	int message_size, int
       errnum, int fildes, const char *pathname, int flags, mode_t mode);

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

   explain_openat
       const char *explain_openat(int fildes, const char *pathname, int	flags,
       mode_t mode);

       The  explain_openat function is used to obtain an explanation of	an er-
       ror returned by the openat(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 openat(2)	system
	       call.

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

       flags   The  original  flags, exactly as	passed to the openat(2)	system
	       call.

       mode    The original mode, exactly as passed to	the  openat(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:
	      int result = openat(fildes, pathname, flags, mode);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_openat(fildes, pathname,
		  flags, mode));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_openat
       const char *explain_errno_openat(int errnum, int	fildes,	const char
       *pathname, int flags, mode_t mode);

       The explain_errno_openat	function is used to obtain an  explanation  of
       an  error  returned by the openat(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 openat(2)	system
	       call.

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

       flags   The  original  flags, exactly as	passed to the openat(2)	system
	       call.

       mode    The original mode, exactly as passed to	the  openat(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:
	      int result = openat(fildes, pathname, flags, mode);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_openat(err, fildes,
		  pathname, flags, mode));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_openat
       void explain_message_openat(char	*message, int message_size, int
       fildes, const char *pathname, int flags,	mode_t mode);

       The explain_message_openat function is used to obtain an	explanation of
       an  error  returned by the openat(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 openat(2)	system
	       call.

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

       flags   The  original  flags, exactly as	passed to the openat(2)	system
	       call.

       mode    The original mode, exactly as passed to	the  openat(2)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      int result = openat(fildes, pathname, flags, mode);
	      if (result < 0)
	      {
		  char message[3000];
		  explain_message_openat(message, sizeof(message), fildes,
		  pathname, flags, mode);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_errno_openat
       void explain_message_errno_openat(char *message,	int message_size, int
       errnum, int fildes, const char *pathname, int flags, mode_t mode);

       The explain_message_errno_openat	function is used to obtain an explana-
       tion of an error	returned by the	openat(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 openat(2)	system
	       call.

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

       flags   The  original  flags, exactly as	passed to the openat(2)	system
	       call.

       mode    The original mode, exactly as passed to	the  openat(2)	system
	       call.

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

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

SEE ALSO
       openat(2)
	       open a file relative to a directory file	descriptor

       explain_openat_or_die(3)
	       open a file relative to a directory file	descriptor and	report
	       errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2013 Peter	Miller

							     explain_openat(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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