1ARES_QUERY(3)              Library Functions Manual              ARES_QUERY(3)
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NAME

6       ares_query - Initiate a single-question DNS query
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SYNOPSIS

9       #include <ares.h>
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11       typedef void (*ares_callback)(void *arg, int status,
12       unsigned char *abuf, int alen)
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14       void ares_query(ares_channel channel, const char *name,
15            int dnsclass, int type, ares_callback callback,
16       void *arg)
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DESCRIPTION

19       The  ares_query  function  initiates a single-question DNS query on the
20       name service channel identified by channel.  The parameter  name  gives
21       the  query name as a NUL-terminated C string of period-separated labels
22       optionally ending with a period; periods and backslashes within a label
23       must  be  escaped  with  a backslash.  The parameters dnsclass and type
24       give the class and type of  the  query  using  the  values  defined  in
25       <arpa/nameser.h>.   When  the query is complete or has failed, the ares
26       library will invoke callback.  Completion or failure of the  query  may
27       happen   immediately,   or   may   happen   during   a  later  call  to
28       ares_process(3) or ares_destroy(3).
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30       The callback argument arg is copied from the ares_query  argument  arg.
31       The callback argument status indicates whether the query succeeded and,
32       if not, how it failed.  It may have any of the following values:
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34       ARES_SUCCESS       The query completed successfully.
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36       ARES_ENODATA       The query completed but contains no answers.
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38       ARES_EFORMERR      The query completed but the server claims  that  the
39                          query was malformatted.
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41       ARES_ESERVFAIL     The  query  completed  but the server claims to have
42                          experienced a failure.  (This code can only occur if
43                          the  ARES_FLAG_NOCHECKRESP  flag  was  specified  at
44                          channel   initialization   time;   otherwise,   such
45                          responses are ignored at the ares_send(3) level.)
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47       ARES_ENOTFOUND     The  query completed but the queried-for domain name
48                          was not found.
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50       ARES_ENOTIMP       The query completed but the server does  not  imple‐
51                          ment  the  operation  requested by the query.  (This
52                          code can only  occur  if  the  ARES_FLAG_NOCHECKRESP
53                          flag  was  specified at channel initialization time;
54                          otherwise,  such  responses  are  ignored   at   the
55                          ares_send(3) level.)
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57       ARES_EREFUSED      The  query  completed  but  the  server  refused the
58                          query.   (This  code   can   only   occur   if   the
59                          ARES_FLAG_NOCHECKRESP  flag was specified at channel
60                          initialization time; otherwise, such  responses  are
61                          ignored at the ares_send(3) level.)
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63       ARES_EBADNAME      The query name name could not be encoded as a domain
64                          name, either  because  it  contained  a  zero-length
65                          label  or  because it contained a label of more than
66                          63 characters.
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68       ARES_ETIMEOUT      No name servers responded within the timeout period.
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70       ARES_ECONNREFUSED  No name servers could be contacted.
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72       ARES_ENOMEM        Memory was exhausted.
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74       ARES_EDESTRUCTION  The name service channel channel is being destroyed;
75                          the query will not be completed.
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77       If  the  query completed (even if there was something wrong with it, as
78       indicated by some of the above error codes), the callback argument abuf
79       points  to  a  result buffer of length alen.  If the query did not com‐
80       plete, abuf will be NULL and alen will be 0.
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SEE ALSO

83       ares_process(3)
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AUTHOR

86       Greg Hudson, MIT Information Systems
87       Copyright 1998 by the Massachusetts Institute of Technology.
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91                                 24 July 1998                    ARES_QUERY(3)