Category: Coding

Listing Modules In Dynamically Linked Shared Object Libraries

We had to rebuild a server over the weekend — it’s a lot harder to get Apache and PHP set up when you don’t have root access to just install things from the yum repository. And, unlike the servers where I built httpd and php from source … we basically relayed requests to the Unix admin to have packages installed. One of the confusions during the whole process was that we didn’t know what to use as the module name for PHP to load in the httpd.conf file. The line from our old server (LoadModule php5_module /etc/httpd/modules/libphp5.so) produced an error that there was no such thing to load.

When a library fails to load with some error, I know to use ldd … but I didn’t know there was a way to list out the modules in a library. Fortunately, one of my coworkers had already run nm and listed out the modules — nm -D –defined-only sharedLibraryFile | grep module — and we were able to identify that the libphp5.so that we had wasn’t anything like the one on the old server. By listing the modules for each of the shared object libraries installed by the php package, we got the proper module name for httpd.conf

Dynamically determining AD Page Size

Question — is it possible to dynamically determine the maximum page size when communicating with AD via LDAP? Since the page size (1) changed between versions and (2) can be user-customized … a guess is sub-optimal.

Answer — yes. If only the default query policy is used, search at
CN=Default Query Policy,CN=Query-Policies,CN=Directory Service,CN=Windows NT,CN=Services,CN=Configuration,*domain naming context* (e.g.
CN=Default Query Policy,CN=Query-Policies,CN=Directory Service,CN=Windows NT,CN=Services,CN=Configuration,DC=example,DC=com) with a filter like “(&(cn=*))”

Return the ldapAdminLimits attribute. Parse MaxPageSize out of the attribute:

lDAPAdminLimits (13): MaxValRange=1500; MaxReceiveBuffer=10485760; MaxDatagramRecv=4096; MaxPoolThreads=4; MaxResultSetSize=262144; MaxTempTableSize=10000; MaxQueryDuration=120; **MaxPageSize=1000**; MaxNotificationPerConn=5; MaxActiveQueries=20; MaxConnIdleTime=900; InitRecvTimeout=120; MaxConnections=5000;

To find all of the query policies, search at CN=Query-Policies,CN=Directory Service,CN=Windows NT,CN=Services,CN=Configuration,*domain naming context* for (&(objectClass=queryPolicy)) … either research a lot about query policies and figure out how to determine which applies to your connection or take the lowest value and know you’re safe.

ADO Notifications

I’ve been underwhelmed with the notifications I get from Azure DevOps – there are a lot of build-centric notifications, but I don’t use ADO for builds or deployment apart from playing around. And I really don’t care if the silly test project I set up to build and deploy a website worked, failed, or whatever. I was thinking about hooking whatever they’re calling Flow this week up to ADO and building notification workflows.

Fortunately, a coworker mentioned that you can customize notifications in ADO … which, I’d spent a few seconds poking around and didn’t see anything. But I spent more than a few seconds this time and happened across this little ellipsis on the card that pops up when I click the circle with my initials in it. More options!

A new menu flies out; and, look, there’s “Notifications”

Exactly as I’ve observed, there are a lot of build-centric alerts. So I created a new subscription.

Here’s a subscription that I hope will notify me when items assigned to me have updates to activity or comments.

HTML Checkbox Adding and Removing Table Row

Here’s the JavaScript code I ended up using to add and remove rows from a table based on a checkbox selection (and only allowing one checkbox per group to be selected). The biggest change is that I added a name and ID to my TR for easier identification. 

$(document).on("change", "input[type='checkbox']", function () {
    var $objCheckbox = $(this);
    if ($objCheckbox.is(":checked")) {			// When checked, deactivate other checkboxes and add to sets to create table
        var objCheckboxGroup = "input:checkbox[tableselector='" + $objCheckbox.attr("tableselector") + "']";

        $(objCheckboxGroup).prop("disabled", true);
        $objCheckbox.prop("disabled", false);		// Allow checked box to be unchecked

        addSetToCreatingTable($objCheckbox.attr("setname"), $objCheckbox.attr("settype"), $objCheckbox.attr("goodcircuits") + "|" + $objCheckbox.attr("value"), $objCheckbox.attr("tableselector"));

    }
    else {							// When unchecked, active checkboxes and remove from sets to create table
        var objCheckboxGroup = "input:checkbox[name='" + $objCheckbox.attr("name") + "']";
        $(objCheckboxGroup).prop("disabled", false);	

        $("#" + $objCheckbox.attr('tableselector')).each(function(){ $(this).remove();})
}
});

HTML Checkboxes To Add and Remove Values from Table

I am creating a web form where the user input sometimes cannot be resolved to a unique value. In those cases, I present the user a set of checkboxes with the options (yes, a radio button makes more sense because you can only select one. But I hate that radio buttons change selection when you hit an arrow key.).

When a selection is made, I need to (1) deactivate the checkboxes for the other options when a checkbox in the group is selected and (2) add information to a data table that is used in subsequent activities.

When a selection is cleared, I need to (1) activate the checkboxes within the group and (2) remove the right row from the data table.

Below is the HTML code that achieves this. Now I just need to map this test page into the actual web code. There’s a post with the actual code I ended up using in production too.

<html>
<head><title>Adding And Removing From Table</title></head>
<body>

<div name="divCircuitClarifications" id="divCircuitClarifications">
  <h3>My-Sample-Circuit-A</h3>
    <input type="checkbox" value="123" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>123</label>
    <input type="checkbox" value="234" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>234</label>
    <input type="checkbox" value="345" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>345</label>
<P>
  <h3>My-Sample-Circuit-B</h3>
    <input type="checkbox" value="abc" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>abc</label>
    <input type="checkbox" value="bcd" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>bcd</label>
    <input type="checkbox" value="cde" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>cde</label>
<P>
  <h3>My-Sample-Circuit-C</h3>
    <input type="checkbox" value="Cabc" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>abc</label>
    <input type="checkbox" value="Cbcd" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>bcd</label>
    <input type="checkbox" value="Ccde" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>cde</label>
<P>
</div>

<div id="divResultTable" name="divResultTable">
<table border="1" padding="1" name="tableSetsToCreate" id="tableSetsToCreate">
	<thead><tr><th>ECCKT</th><th>Circuit ID</th></tr></thead>
	<tbody></tbody>
</table>


<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<script>
	$("input:checkbox").on('click', function() {
	  	var $objCheckbox = $(this);
	  	if ($objCheckbox.is(":checked")) {			// When checked, deactivate other checkboxes and add to sets to create table
	    		var objCheckboxGroup = "input:checkbox[tableselector='" + $objCheckbox.attr("tableselector") + "']";
	
	    		$(objCheckboxGroup).prop("disabled", true);
	    		$objCheckbox.prop("disabled", false);		// Allow checked box to be unchecked

	                var strTableRowString = '<tr><td>' + $objCheckbox.attr("tableselector") + '</td><td>' + $objCheckbox.val() + '</td>\n';
	                $('#tableSetsToCreate tbody').append(strTableRowString);
	  	}
		else {							// When unchecked, active checkboxes and remove from sets to create table
	    		var objCheckboxGroup = "input:checkbox[name='" + $objCheckbox.attr("name") + "']";
	    		$(objCheckboxGroup).prop("disabled", false);	

			$("tr:contains('" + $objCheckbox.attr('tableselector') + "')").each(function(){ $(this).remove();})
  		}
	});
</script>
</body>

Kid Coding

I’ve seen a number of articles written by developers and IT folks promoting how they won’t be teaching their young kid to code. Of all of the arguments against teaching kids to code, the only one that really strikes me is the fact that a lot of parents don’t know how to code themselves. Now, I expect it is possible to not know French but manage to cobble together some approach to teaching your kid French. It’s a lot easier (and the results are apt to be better) if you actually know some French. My decision to teach my daughter to code doesn’t mean it’s a vital skill that every kid needs to learn to prepare them for future jobs. But, since it is something I do, it is something I share with my daughter. If she weren’t interested in what is going on beyond getting it all typed in, I’d stop. But she’s interested in exploring beyond what the coding book tells her to type. As we created a little character on the screen, Anya wondered if we could make different little figures. At different locations. In different sizes. In different colors. In using Scratch, she develops characters and game play.

Why teach a seven year old kid to code? Why do you teach your kids anything apart from the mandatory school curriculum? Working on the car? She can help and learn a bit about how vehicles work. I replaced the tube on my bicycle tire, and she helped. She was aware that bicycle tires had replaceable tubes that could explode on you … which was useful knowledge when she blew out her own tube. She sews with me — embroidery and a machine — because being able to patch clothes saves having to replace things as frequently. Mowing the lawn – she’s aware that a house with a lot of land requires work and knows how to safely operate both the push and riding mowers. Gardening – she knows where food comes from, how to grow her own, and how much work actually goes into feeding the country. She’ll participate in chicken keeping – somewhat so she knows where eggs come from and the amount of work that goes into egg production, but also because pets are fun (and our chickens will certainly be more socialized with her involvement). We share all sorts of activities with our daughter because we enjoy them. Some intrigue her, some don’t. But how do you learn where your interests are if your exposure is limited to reading and math for the first decade, then science and history for the next almost decade?

All of that provides useful, practical knowledge. And learning to code is certainly useful and practical. But the utility of such knowledge, the practicality of such knowledge isn’t the reason I am teaching my daughter to code. Or, for that matter, the reason I’ve taught her anything else at home. These activities involve deductive reasoning, analytical thought, problem solving, research skills, or accepting instruction from others. All of which are generally useful in life.

PHP Sub-Second Sleep

I needed to add a sleep to a PHP process, but I didn’t want to waste a whole second on each cycle. That’s usleep:

<?php
        date_default_timezone_set('America/New_York');

        $t = microtime(true);
        $micro = sprintf("%06d",($t - floor($t)) * 1000000);
        $d = new DateTime( date('Y-m-d H:i:s.'.$micro, $t) );

        print $d->format("Y-m-d H:i:s.u") . "\n";                                                                       
        usleep(100000);

        $t = microtime(true);
        $micro = sprintf("%06d",($t - floor($t)) * 1000000);
        $d = new DateTime( date('Y-m-d H:i:s.'.$micro, $t) );

        print $d->format("Y-m-d H:i:s.u")  . "\n";                                                                      
        sleep(1);
        $t = microtime(true);
        $micro = sprintf("%06d",($t - floor($t)) * 1000000);
        $d = new DateTime( date('Y-m-d H:i:s.'.$micro, $t) );

        print $d->format("Y-m-d H:i:s.u")  . "\n";                                                                      
?>

Run the script, and you’ll see sub-second sleeps.

[tempuser@564240601ac2 /]# php testSleep.php
2020-07-09 14:06:20.641449
2020-07-09 14:06:20.741952
2020-07-09 14:06:21.742347

HTML – Multiple Values on Select Option

I needed to pass multiple values with a select option. It’s easily accomplished by setting the value to a JSON string

while ($row = oci_fetch_array($stmt, OCI_ASSOC+OCI_RETURN_NULLS)) {
	echo "<option value= " . json_encode($row) . ">" . $row['STRTYPENAME'] . "</option>\n";
}

And using JSON.parse to pull out the key of the value you need:

jQuery("#selectDivSetType").change(function () {     
    var strTemplateObject = $('#selectDivSetType').val();
    var jsonTemplateObject = JSON.parse( strTemplateObject );
    var strTemplateURI = './templates/' + jsonTemplateObject.STRTEMPLATENAME;
    $('#templateURI').attr("href", strTemplateURI); 
});

jQuery – Changing href When Drop-down Selection Changes

I needed to provide a different template depending on the type of activity selected in a drop-down menu. The following jQuery code gets the template name from the drop-down value and updates the href target. 

jQuery("#selectDivSetType").change(function () {     
    var strTemplateName = $('#selectDivSetType').val();
    var strTemplateURI = './templates/' + strTemplateName;
    $('#templateURI').attr("href", strTemplateURI); 
});

Scratch: Changing Variable In Operator

When I needed to change a variable within an operator block, I’d been removing the variable block and adding the right one. Unlike the “change <variable> …” and “set <variable>…” blocks, the little variable name bubbles do not have a drop-down selector. Today, Anya and I were working on our Chicken Keepers games and she right-clicked the little bubble to select a different variable. Totally didn’t realize you could do that.