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explain_poll(3)		   Library Functions Manual	       explain_poll(3)

NAME
       explain_poll - explain poll(2) errors

SYNOPSIS
       #include	<libexplain/poll.h>
       const char *explain_poll(struct pollfd *fds, int	nfds, int timeout);
       const char *explain_errno_poll(int errnum, struct pollfd	*fds, int
       nfds, int timeout);
       void explain_message_poll(char *message,	int message_size, struct
       pollfd *fds, int	nfds, int timeout);
       void explain_message_errno_poll(char *message, int message_size,	int
       errnum, struct pollfd *fds, int nfds, int timeout);

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

   explain_poll
       const char *explain_poll(struct pollfd *fds, int	nfds, int timeout);

       The  explain_poll function is used to obtain an explanation of an error
       returned	by the poll(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.

       fds     The original fds, exactly as passed to the poll(2) system call.

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

       timeout The original timeout, exactly as	passed to the  poll(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 = poll(fds, nfds, timeout);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_poll(fds, nfds, timeout));
		  exit(EXIT_FAILURE);
	      }

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

   explain_errno_poll
       const char *explain_errno_poll(int errnum, struct pollfd	*fds, int
       nfds, int timeout);

       The  explain_errno_poll function	is used	to obtain an explanation of an
       error returned by the poll(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.

       fds     The original fds, exactly as passed to the poll(2) system call.

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

       timeout The  original  timeout, exactly as passed to the	poll(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 = poll(fds, nfds, timeout);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_poll(err, fds, nfds,
		  timeout));
		  exit(EXIT_FAILURE);
	      }

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

   explain_message_poll
       void explain_message_poll(char *message,	int message_size, struct
       pollfd *fds, int	nfds, int timeout);

       The  explain_message_poll  function is used to obtain an	explanation of
       an error	returned by the	poll(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.

       fds     The original fds, exactly as passed to the poll(2) system call.

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

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

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

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

   explain_message_errno_poll
       void explain_message_errno_poll(char *message, int message_size,	int
       errnum, struct pollfd *fds, int nfds, int timeout);

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

       fds     The original fds, exactly as passed to the poll(2) system call.

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

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

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

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

SEE ALSO
       poll(2) wait for	some event on a	file descriptor

       explain_poll_or_die(3)
	       wait for	some event on a	file descriptor	and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2010 Peter	Miller

							       explain_poll(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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