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explain_dirfd(3)	   Library Functions Manual	      explain_dirfd(3)

NAME
       explain_dirfd - explain dirfd(3)	errors

SYNOPSIS
       #include	<libexplain/dirfd.h>
       const char *explain_dirfd(DIR *dir);
       const char *explain_errno_dirfd(int errnum, DIR *dir);
       void explain_message_dirfd(char *message, int message_size, DIR *dir);
       void explain_message_errno_dirfd(char *message, int message_size, int
       errnum, DIR *dir);

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

   explain_dirfd
       const char *explain_dirfd(DIR *dir);

       The explain_dirfd function is used to obtain an explanation of an error
       returned	by the dirfd(3)	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.

       dir     The  original  dir,  exactly  as	 passed	to the dirfd(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:
	      int result = dirfd(dir);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_dirfd(dir));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_dirfd
       const char *explain_errno_dirfd(int errnum, DIR *dir);

       The explain_errno_dirfd function	is used	to obtain an explanation of an
       error returned by the dirfd(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.

       dir     The original dir, exactly as  passed  to	 the  dirfd(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:
	      int result = dirfd(dir);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_dirfd(err, dir));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_dirfd
       void explain_message_dirfd(char *message, int message_size, DIR *dir);

       The explain_message_dirfd function is used to obtain an explanation  of
       an  error  returned  by the dirfd(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.

       dir     The  original  dir,  exactly  as	 passed	to the dirfd(3)	system
	       call.

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

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

   explain_message_errno_dirfd
       void explain_message_errno_dirfd(char *message, int message_size, int
       errnum, DIR *dir);

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

       dir     The  original  dir,  exactly  as	 passed	to the dirfd(3)	system
	       call.

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

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

SEE ALSO
       dirfd(3)
	       get directory stream file descriptor

       explain_dirfd_or_die(3)
	       get directory stream file descriptor and	report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2009 Peter	Miller

							      explain_dirfd(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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