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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
       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
       following 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_listen_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,
               including other threads.

       Note: This function is not thread safe,  because  it  shares  a  return
       buffer 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
       following 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_listen_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,
               including other threads.

       Note: This function is not thread safe,  because  it  shares  a  return
       buffer 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
       explanation  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
       following 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_listen_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
               returned 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
       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
       following 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_listen_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
               returned 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 0.19
       Copyright (C) 2008 Peter Miller

                                                             explain_listen(3)