path: root/ares_gethostbyname.3
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authorDaniel Stenberg <>2003-10-07 21:54:04 (GMT)
committerDaniel Stenberg <>2003-10-07 21:54:04 (GMT)
commit5e847a14bd65383ce65f143c578e120899981fd9 (patch)
tree0072e647fe22e05aee94cf4e4bf101209e30626c /ares_gethostbyname.3
ares 1.1.1 with collected applied patches
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+.\" $Id$
+.\" Copyright 1998 by the Massachusetts Institute of Technology.
+.\" Permission to use, copy, modify, and distribute this
+.\" software and its documentation for any purpose and without
+.\" fee is hereby granted, provided that the above copyright
+.\" notice appear in all copies and that both that copyright
+.\" notice and this permission notice appear in supporting
+.\" documentation, and that the name of M.I.T. not be used in
+.\" advertising or publicity pertaining to distribution of the
+.\" software without specific, written prior permission.
+.\" M.I.T. makes no representations about the suitability of
+.\" this software for any purpose. It is provided "as is"
+.\" without express or implied warranty.
+.TH ARES_GETHOSTBYNAME 3 "25 July 1998"
+ares_gethostbyname \- Initiate a host query by name
+.B #include <ares.h>
+.B typedef void (*ares_host_callback)(void *\fIarg\fP, int \fIstatus\fP,
+.B struct hostent *\fIhostent\fP)
+.B void ares_gethostbyname(ares_channel \fIchannel\fP, const char *\fIname\fP,
+.B int \fIfamily\fP, ares_host_callback \fIcallback\fP, void *\fIarg\fP)
+.B ares_gethostbyname
+function initiates a host query by name on the name service channel
+identified by
+.IR channel .
+The parameter
+.I name
+gives the hostname as a NUL-terminated C string, and
+.I family
+gives the desired type of address for the resulting host entry. When
+the query is complete or has failed, the ares library will invoke
+.IR callback .
+Completion or failure of the query may happen immediately, or may
+happen during a later call to
+.BR ares_process (3)
+.BR ares_destroy (3).
+The callback argument
+.I arg
+is copied from the
+.B ares_gethostbyname
+.IR arg .
+The callback argument
+.I status
+indicates whether the query succeeded and, if not, how it failed. It
+may have any of the following values:
+.TP 19
+The host lookup completed successfully.
+.TP 19
+The ares library does not know how to find addresses of type
+.IR family .
+.TP 19
+The hostname
+.B name
+is composed entirely of numbers and periods, but is not a valid
+representation of an Internet address.
+.TP 19
+The address
+.I addr
+was not found.
+.TP 19
+Memory was exhausted.
+.TP 19
+The name service channel
+.I channel
+is being destroyed; the query will not be completed.
+On successful completion of the query, the callback argument
+.I hostent
+points to a
+.B struct hostent
+containing the name of the host returned by the query. The callback
+need not and should not attempt to free the memory pointed to by
+.IR hostent ;
+the ares library will free it when the callback returns. If the query
+did not complete successfully,
+.I hostent
+will be
+.BR ares_process (3)
+Greg Hudson, MIT Information Systems
+Copyright 1998 by the Massachusetts Institute of Technology.