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explain_select(3)	   Library Functions Manual	     explain_select(3)

NAME
       explain_select -	explain	select(2) errors

SYNOPSIS
       #include	<sys/select.h> #include	<libexplain/select.h>
       const char *explain_select(int nfds, fd_set *readfds, fd_set *writefds,
       fd_set *exceptfds, struct timeval *timeout);
       const char *explain_errno_select(int errnum, int	nfds, fd_set *readfds,
       fd_set *writefds, fd_set	*exceptfds, struct timeval *timeout);
       void  explain_message_select(char *message, int message_size, int nfds,
       fd_set *readfds,	fd_set *writefds, fd_set  *exceptfds,  struct  timeval
       *timeout);
       void  explain_message_errno_select(char *message, int message_size, int
       errnum, int nfds, fd_set	*readfds, fd_set *writefds, fd_set *exceptfds,
       struct timeval *timeout);

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

   explain_select
       const char *explain_select(int nfds, fd_set *readfds, fd_set *writefds,
       fd_set *exceptfds, struct timeval *timeout);

       The  explain_select function is used to obtain an explanation of	an er-
       ror returned by the select(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.

       This  function  is intended to be used in a fashion similar to the fol-
       lowing example:
	      if (select(nfds, readfds,	writefds, exceptfds, timeout) <	0)
	      {
		  fprintf(stderr, "%s\n", explain_select(nfds,
		      readfds, writefds, exceptfds, timeout));
		  exit(EXIT_FAILURE);
	      }

       nfds    The original nfds, exactly as passed to	the  select(2)	system
	       call.

       readfds The original readfds, exactly as	passed to the select(2)	system
	       call.

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

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

       timeout The original timeout, exactly as	passed to the select(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,  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_select
       const char *explain_errno_select(int errnum, int	nfds, fd_set *readfds,
       fd_set *writefds, fd_set	*exceptfds, struct timeval *timeout);

       The  explain_errno_select  function is used to obtain an	explanation of
       an error	returned by the	select(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:
	      if (select(nfds, readfds,	writefds, exceptfds, timeout) <	0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_select(err,
		      nfds, readfds, writefds, exceptfds, timeout));
		  exit(EXIT_FAILURE);
	      }

       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.

       nfds    The  original  nfds,  exactly as	passed to the select(2)	system
	       call.

       readfds The original readfds, exactly as	passed to the select(2)	system
	       call.

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

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

       timeout The original timeout, exactly as	passed to the select(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, 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_select
       void  explain_message_select(char *message, int message_size, int nfds,
       fd_set *readfds,	fd_set *writefds, fd_set  *exceptfds,  struct  timeval
       *timeout);

       The  explain_message_select function may	be used	to  obtain an explana-
       tion of an error	returned by the	select(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.

       This  function  is intended to be used in a fashion similar to the fol-
       lowing example:
	      if (select(nfds, readfds,	writefds, exceptfds, timeout) <	0)
	      {
		  char message[3000];
		  explain_message_select(message, sizeof(message),
		      nfds, readfds, writefds, exceptfds, timeout);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       message The location in which to	store  the  returned  message.	 If  a
	       suitable	 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.

       nfds    The  original  nfds,  exactly as	passed to the select(2)	system
	       call.

       readfds The original readfds, exactly as	passed to the select(2)	system
	       call.

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

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

       timeout The original timeout, exactly as	passed to the select(2)	system
	       call.

   explain_message_errno_select
       void explain_message_errno_select(char *message,	int message_size,  int
       errnum, int nfds, fd_set	*readfds, fd_set *writefds, fd_set *exceptfds,
       struct timeval *timeout);

       The explain_message_errno_select	function may be	used to	obtain an  ex-
       planation of an error returned by the select(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:
	      if (select(nfds, readfds,	writefds, exceptfds, timeout) <	0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_select(message,	sizeof(message), err,
		      nfds, readfds, writefds, exceptfds, timeout);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       message The  location  in  which	 to  store the returned	message.  If a
	       suitable	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.

       nfds    The original nfds, exactly as passed to	the  select(2)	system
	       call.

       readfds The original readfds, exactly as	passed to the select(2)	system
	       call.

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

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

       timeout The original timeout, exactly as	passed to the select(2)	system
	       call.

SEE ALSO
       select(2)
	       blah blah

       explain_select_or_die(3)
	       blah blah and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							     explain_select(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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