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explain_gethostbyname(3)   Library Functions Manual   explain_gethostbyname(3)

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 mes-
       sage_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 buf-
       fer 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_geth-
       ostbyname_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  explana-
       tion  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 buf-
       fer 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_geth-
       ostbyname_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	expla-
       nation  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 suit-
	       able 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.

       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_geth-
       ostbyname_or_die(3) function.

   explain_message_errno_gethostbyname
       void explain_message_errno_gethostbyname(char *message, int mes-
       sage_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 suit-
	       able 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.

       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(mes-
		  sage), err, name);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The  above  code	example	is available pre-packaged as the explain_geth-
       ostbyname_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 1.3
       Copyright (C) 2013 Peter	Miller

						      explain_gethostbyname(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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