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NAME

       explain_gethostname - explain gethostname(2) errors

SYNOPSIS

       #include <libexplain/gethostname.h>
       const char *explain_gethostname(char *data, size_t data_size);
       const  char  *explain_errno_gethostname(int  errnum, char *data, size_t
       data_size);
       void explain_message_gethostname(char *message, int message_size,  char
       *data, size_t data_size);
       void explain_message_errno_gethostname(char *message, int message_size,
       int errnum, char *data, size_t data_size);

DESCRIPTION

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

   explain_gethostname
       const char *explain_gethostname(char *data, size_t data_size);

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

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

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

       data_size
               The original data_size, exactly as passed to the gethostname(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_gethostname
       const char *explain_errno_gethostname(int errnum,  char  *data,  size_t
       data_size);

       The explain_errno_gethostname function is used to obtain an explanation
       of an error returned by the gethostname(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.

       This  function  is  intended  to  be  used  in a fashion similar to the
       following example:
              if (gethostname(data, data_size) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_gethostname(err, data, data_size));
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_gethostname_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.

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

       data_size
               The original data_size, exactly as passed to the gethostname(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_gethostname
       void explain_message_gethostname(char *message, int message_size,  char
       *data, size_t data_size);

       The   explain_message_gethostname   function   is  used  to  obtain  an
       explanation of an error returned by  the  gethostname(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 (gethostname(data, data_size) < 0)
              {
                  char message[3000];
                  explain_message_gethostname(message, sizeof(message), data, data_size);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_gethostname_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.

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

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

   explain_message_errno_gethostname
       void explain_message_errno_gethostname(char *message, int message_size,
       int errnum, char *data, size_t data_size);

       The explain_message_errno_gethostname function is  used  to  obtain  an
       explanation  of  an  error  returned by the gethostname(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.

       This function is intended to be  used  in  a  fashion  similar  to  the
       following example:
              if (gethostname(data, data_size) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_gethostname(message, sizeof(message), err, data,
                      data_size);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The   above   code   example   is   available   pre-packaged   as   the
       explain_gethostname_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.

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

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

SEE ALSO

       gethostname(2)
               get/set hostname

       explain_gethostname_or_die(3)
               get/set hostname and report errors

COPYRIGHT

       libexplain version 0.19
       Copyright (C) 2009 Peter Miller

                                                        explain_gethostname(3)