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NAME

       explain_getsockopt - explain getsockopt(2) errors

SYNOPSIS

       #include <libexplain/getsockopt.h>
       const  char  *explain_getsockopt(int  fildes, int level, int name, void
       *data, socklen_t *data_size);
       const char *explain_errno_getsockopt(int errnum, int fildes, int level,
       int name, void *data, socklen_t *data_size);
       void  explain_message_getsockopt(char  *message,  int message_size, int
       fildes, int level, int name, void *data, socklen_t *data_size);
       void explain_message_errno_getsockopt(char *message, int  message_size,
       int  errnum,  int  fildes,  int  level, int name, void *data, socklen_t
       *data_size);

DESCRIPTION

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

   explain_getsockopt
       const  char  *explain_getsockopt(int  fildes, int level, int name, void
       *data, socklen_t *data_size);

       The explain_getsockopt function is used to obtain an explanation of  an
       error returned by the getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
              {
                  fprintf(stderr, "%s\n", explain_getsockopt(fildes,
                      level, name, data, data_size));
                  exit(EXIT_FAILURE);
              }

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

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

       level   The  original  level,  exactly  as  passed to the getsockopt(2)
               system call.

       name    The original name,  exactly  as  passed  to  the  getsockopt(2)
               system call.

       data    The  original  data,  exactly  as  passed  to the getsockopt(2)
               system call.

       data_size
               The original data_size, exactly as passed to the  getsockopt(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_getsockopt
       const char *explain_errno_getsockopt(int errnum, int fildes, int level,
       int name, void *data, socklen_t *data_size);

       The  explain_errno_getsockopt function is used to obtain an explanation
       of an error returned by the getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_getsockopt(err,
                      fildes, level, name, data, data_size));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getsockopt_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 getsockopt(2)
               system call.

       level   The original level, exactly  as  passed  to  the  getsockopt(2)
               system call.

       name    The  original  name,  exactly  as  passed  to the getsockopt(2)
               system call.

       data    The original data,  exactly  as  passed  to  the  getsockopt(2)
               system call.

       data_size
               The  original data_size, exactly as passed to the getsockopt(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_getsockopt
       void  explain_message_getsockopt(char  *message,  int message_size, int
       fildes, int level, int name, void *data, socklen_t *data_size);

       The explain_message_getsockopt function  may  be  used  to   obtain  an
       explanation of an error returned by the getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
              {
                  char message[3000];
                  explain_message_getsockopt(message, sizeof(message),
                      fildes, level, name, data, data_size);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getsockopt_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  getsockopt(2)
               system call.

       level   The  original  level,  exactly  as  passed to the getsockopt(2)
               system call.

       name    The original name,  exactly  as  passed  to  the  getsockopt(2)
               system call.

       data    The  original  data,  exactly  as  passed  to the getsockopt(2)
               system call.

       data_size
               The original data_size, exactly as passed to the  getsockopt(2)
               system call.

   explain_message_errno_getsockopt
       void  explain_message_errno_getsockopt(char *message, int message_size,
       int errnum, int fildes, int level,  int  name,  void  *data,  socklen_t
       *data_size);

       The  explain_message_errno_getsockopt function may be used to obtain an
       explanation of an error returned by the getsockopt(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 (getsockopt(fildes, level, name, data, data_size) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_getsockopt(message, sizeof(message),
                      err, fildes, level, name, data, data_size);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_getsockopt_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  getsockopt(2)
               system call.

       level   The  original  level,  exactly  as  passed to the getsockopt(2)
               system call.

       name    The original name,  exactly  as  passed  to  the  getsockopt(2)
               system call.

       data    The  original  data,  exactly  as  passed  to the getsockopt(2)
               system call.

       data_size
               The original data_size, exactly as passed to the  getsockopt(2)
               system call.

SEE ALSO

       getsockopt(2)
               get and set options on sockets

       explain_getsockopt_or_die(3)
               get and set options on sockets and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                         explain_getsockopt(3)