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explain_listen(3)	   Library Functions Manual	     explain_listen(3)

NAME
       explain_listen -	explain	listen(2) errors

SYNOPSIS
       #include	<libexplain/listen.h>
       const char *explain_listen(int fildes, int backlog);
       const char *explain_errno_listen(int errnum, int	fildes,	int backlog);
       void   explain_message_listen(char   *message,  int  message_size,  int
       fildes, int backlog);
       void explain_message_errno_listen(char *message,	int message_size,  int
       errnum, int fildes, int backlog);

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

   explain_listen
       const char *explain_listen(int fildes, int backlog);

       The explain_listen function is used to obtain an	explanation of an  er-
       ror  returned by	the listen(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 (listen(fildes, backlog) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_listen(fildes, backlog));
		  exit(EXIT_FAILURE);
	      }

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

       fildes  The original fildes, exactly as passed to the listen(2)	system
	       call.

       backlog The original backlog, exactly as	passed to the listen(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_listen
       const char *explain_errno_listen(int errnum, int	fildes,	int backlog);

       The  explain_errno_listen  function is used to obtain an	explanation of
       an error	returned by the	listen(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 (listen(fildes, backlog) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_listen(err, fildes, backlog));
		  exit(EXIT_FAILURE);
	      }

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

       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 listen(2)	system
	       call.

       backlog The original backlog, exactly as	passed to the listen(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_listen
       void   explain_message_listen(char   *message,  int  message_size,  int
       fildes, int backlog);

       The explain_message_listen function may be used to  obtain an  explana-
       tion  of	an error returned by the listen(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 (listen(fildes, backlog) < 0)
	      {
		  char message[3000];
		  explain_message_listen(message, sizeof(message), fildes, backlog);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

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

       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.

       fildes  The  original fildes, exactly as	passed to the listen(2)	system
	       call.

       backlog The original backlog, exactly as	passed to the listen(2)	system
	       call.

   explain_message_errno_listen
       void  explain_message_errno_listen(char *message, int message_size, int
       errnum, int fildes, int backlog);

       The explain_message_errno_listen	function may be	used to	obtain an  ex-
       planation of an error returned by the listen(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 (listen(fildes, backlog) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_listen(message,	sizeof(message), err,
		      fildes, backlog);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

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

       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.

       fildes  The  original fildes, exactly as	passed to the listen(2)	system
	       call.

       backlog The original backlog, exactly as	passed to the listen(2)	system
	       call.

SEE ALSO
       listen(2)
	       listen for connections on a socket

       explain_listen_or_die(3)
	       listen for connections on a socket and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							     explain_listen(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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