Provided by: libexplain-dev_1.4.D001-13_amd64 bug

NAME

       explain_gethostbyname - explain gethostbyname(3) errors

SYNOPSIS

       #include <libexplain/gethostbyname.h>
       const char *explain_gethostbyname(const char *name);
       const char *explain_errno_gethostbyname(int errnum, const char *name);
       void explain_message_gethostbyname(char *message, int message_size, const char *name);
       void explain_message_errno_gethostbyname(char *message, int message_size, int errnum,
       const char *name);

DESCRIPTION

       These  functions  may  be  used  to  obtain  explanations  for  errors  returned  by   the
       gethostbyname(3) system call.

   explain_gethostbyname
       const char *explain_gethostbyname(const char *name);

       The  explain_gethostbyname  function is used to obtain an explanation of an error returned
       by the gethostbyname(3) 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.

       name    The original name, exactly as passed to the gethostbyname(3) 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.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              struct hostent *result = gethostbyname(name);
              if (!result)
              {
                  fprintf(stderr, "%s\n", explain_gethostbyname(name));
                  exit(EXIT_FAILURE);
              }

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

   explain_errno_gethostbyname
       const char *explain_errno_gethostbyname(int errnum, const char *name);

       The explain_errno_gethostbyname function is used to obtain  an  explanation  of  an  error
       returned  by  the  gethostbyname(3) 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.

       name    The original name, exactly as passed to the gethostbyname(3) 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.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              struct hostent *result = gethostbyname(name);
              if (!result)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n", explain_errno_gethostbyname(err, name));
                  exit(EXIT_FAILURE);
              }

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

   explain_message_gethostbyname
       void explain_message_gethostbyname(char *message, int message_size, const char *name);

       The explain_message_gethostbyname function is used to obtain an explanation  of  an  error
       returned  by  the  gethostbyname(3) 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 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.

       name    The original name, exactly as passed to the gethostbyname(3) system call.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              struct hostent *result = gethostbyname(name);
              if (!result)
              {
                  char message[3000];
                  explain_message_gethostbyname(message, sizeof(message), name);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

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

   explain_message_errno_gethostbyname
       void explain_message_errno_gethostbyname(char *message, int message_size, int errnum,
       const char *name);

       The  explain_message_errno_gethostbyname  function  is used to obtain an explanation of an
       error returned by the gethostbyname(3) 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 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.

       name    The original name, exactly as passed to the gethostbyname(3) system call.

       Example: This function is intended to be used  in  a  fashion  similar  to  the  following
       example:
              struct hostent *result = gethostbyname(name);
              if (!result)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_gethostbyname(message, sizeof(message), err, name);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

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

SEE ALSO

       gethostbyname(3)
               get host address given host name

       explain_gethostbyname_or_die(3)
               get host address given host name and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2013 Peter Miller

                                                                         explain_gethostbyname(3)