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<div id="projectname">net-snmp
 <span id="projectnumber">5.4.1</span>
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<div class="title">watched.c</div> </div>
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<p>These examples creates some scalar registrations that allows some simple variables to be accessed via SNMP. In a more realistic example, it is likely that these variables would also be manipulated in other ways outside of SNMP gets/sets.</p>
<div class="fragment"><pre class="fragment"><span class="comment">/*</span>
<span class="comment"> * watched.c</span>
<span class="comment"> * $Id: watched.c 12097 2005-04-20 18:03:47Z rstory $</span>
<span class="comment"> *</span>
<span class="comment"> */</span>
<span class="comment">/*</span>
<span class="comment"> * start by including the appropriate header files </span>
<span class="comment"> */</span>
<span class="preprocessor">#include <net-snmp/net-snmp-config.h></span>
<span class="preprocessor">#include <net-snmp/net-snmp-includes.h></span>
<span class="preprocessor">#include <net-snmp/agent/net-snmp-agent-includes.h></span>
<span class="keywordtype">void</span> init_watched_string(<span class="keywordtype">void</span>);
<span class="keywordtype">void</span> init_watched(<span class="keywordtype">void</span>)
{
init_watched_string();
}
<span class="keywordtype">void</span> init_watched_string(<span class="keywordtype">void</span>)
{
<span class="comment">/*</span>
<span class="comment"> * the storage for our string. It must be static or allocated.</span>
<span class="comment"> * we use static here for simplicity.</span>
<span class="comment"> */</span>
<span class="keyword">static</span> <span class="keywordtype">char</span> my_string[256] = <span class="stringliteral">"So long, and thanks for all the fish!"</span>;
<span class="comment">/*</span>
<span class="comment"> * the OID we want to register our string at. This should be a</span>
<span class="comment"> * fully qualified instance. In our case, it's a scalar at:</span>
<span class="comment"> * NET-SNMP-EXAMPLES-MIB::netSnmpExampleString.0 (note the trailing</span>
<span class="comment"> * 0 which is required for any instantiation of any scalar object) </span>
<span class="comment"> */</span>
oid my_registration_oid[] =
{ 1, 3, 6, 1, 4, 1, 8072, 2, 1, 3, 0 };
<span class="comment">/*</span>
<span class="comment"> * variables needed for registration</span>
<span class="comment"> */</span>
<a name="_a0"></a><a class="code" href="structnetsnmp__handler__registration__s.html" title="Root registration info.">netsnmp_handler_registration</a> *reginfo;
<a name="_a1"></a><a class="code" href="structnetsnmp__watcher__info__s.html">netsnmp_watcher_info</a> *watcher_info;
<span class="keywordtype">int</span> watcher_flags;
<span class="comment">/*</span>
<span class="comment"> * a debugging statement. Run the agent with -Dexample_string_instance</span>
<span class="comment"> * to see the output of this debugging statement. </span>
<span class="comment"> */</span>
DEBUGMSGTL((<span class="stringliteral">"example_string_instance"</span>,
<span class="stringliteral">"Initalizing example string instance. Default value = %s\n"</span>,
my_string));
<span class="comment">/*</span>
<span class="comment"> * create the registration info for our string. If you want to</span>
<span class="comment"> *</span>
<span class="comment"> * If we wanted a callback when the value was retrieved or set</span>
<span class="comment"> * (even though the details of doing this are handled for you),</span>
<span class="comment"> * you could change the NULL pointer below to a valid handler</span>
<span class="comment"> * function.</span>
<span class="comment"> *</span>
<span class="comment"> * Change RWRITE to RONLY for a read-only string.</span>
<span class="comment"> */</span>
reginfo = netsnmp_create_handler_registration(<span class="stringliteral">"my example string"</span>, NULL,
my_registration_oid,
OID_LENGTH(my_registration_oid),
HANDLER_CAN_RWRITE);
<span class="comment">/*</span>
<span class="comment"> * the two options for a string watcher are:</span>
<span class="comment"> * fixed size string (length never changes)</span>
<span class="comment"> * variable size (length can be 0 - MAX, for some MAX)</span>
<span class="comment"> *</span>
<span class="comment"> * we'll use a variable length string.</span>
<span class="comment"> */</span>
watcher_flags = WATCHER_MAX_SIZE;
<span class="comment">/*</span>
<span class="comment"> * create the watcher info for our string, and set the max size.</span>
<span class="comment"> */</span>
watcher_info =
netsnmp_create_watcher_info(my_string, strlen(my_string),
ASN_OCTET_STR, watcher_flags);
watcher_info-><a name="a2"></a>max_size = <span class="keyword">sizeof</span>(my_string);
<span class="comment">/*</span>
<span class="comment"> * the line below registers our "my_string" variable above as</span>
<span class="comment"> * accessible and makes it writable. </span>
<span class="comment"> * </span>
<span class="comment"> * If we wanted a callback when the value was retrieved or set</span>
<span class="comment"> * (even though the details of doing this are handled for you),</span>
<span class="comment"> * you could change the NULL pointer below to a valid handler</span>
<span class="comment"> * function. </span>
<span class="comment"> */</span>
netsnmp_register_watched_instance(reginfo, watcher_info);
DEBUGMSGTL((<span class="stringliteral">"example_string_instance"</span>,
<span class="stringliteral">"Done initalizing example string instance\n"</span>));
}
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