Gregory Porter's Blog

Let’s say you are using Vim and you have two buffers open and you’d like to open the buffer into a split

All you have to do is:

:vert sb N

Where N is the number of the buffer you want ( use :buffers to find the number of the buffer)

I’m working on an Angular application that runs in IE and sets a Local Storage value when the tab closes.

It hooks into the $window.onunload event.

I was having trouble however, verifying that the value was being set correctly. If I brought up the app and then closed the tab or the browser, the whole thing would close before I had the chance to inspect the localStorage value.

The solution was to set a ‘storage’ breakpoint and just navigate to another page, rather than closing the whole page or window. If you close the browser, I guess the closing of the browser takes precedence over console logs. In any case, to do this, follow the following steps:

1) Open the Debugger tab of the Dev Tools.

2) Under the Watches Breakpoints section click on “Add event breakpoint”

3) Expand the “Event” dropdown (it defaults to “Mouse Events”)

4) Select “storage” which can be found under the “Media” section (it’s towards the bottom)

5) Under “Watches” click “Add watch”

6) Type “localStorage” (without the quotations) and press Enter

To see this in action, navigate from your current webpage (the one you want to inspect) to another page (like Google.com). The storage event will trigger and you’ll see the values of localStorage.

I was trying to run my local Node server but I kept seeing the following error

I rebuild the application and reinstalled all the npm dependancies but I kept seeing this EADDRINUSE error

The solution is to kill all my local gulp tasks and make sure that the server is killed

Open another terminal and run:

ps -ax | grep node

You’ll see something like:

75453 ttys001    0:00.68 node ./api/server.js

75857 ttys004    0:00.00 grep node

Then run:

sudo kill 75453

That 75453 is the process number that corresponds to your server.

You should now be able to run your servers again

Note - This error might also mean that another process is using the port that your Node server is trying to use so you can also trying change your servers port number to something that isn't in use. In my case, I knew that the solution wasn't just changing the port number.

In vim, to copy a specific line:

:line-you-want-to-yank y

So if I wanted to copy line 40, I would type:

:40 y

If you are working in Windows and sometimes use the Command Line, it can be useful to start the CL in your project folder.

Click on the Start Menu

Find the Windows Command Processor shortcut

Right click on the shortcut

Select Properties which will cause a Properties window to popup

Find the section that says “Start in:” (the default is probably C:\Windows\System32) and change the value to your project’s directory

Click Apply

Neat trick to read JSON on the command line.

If you want to see the Angular scope of an element on a page, in Chrome.

1) Right click on the element and select “Inspect Element”

2) The Developer Tools should pop up

3) Select “Console” and enter “angular.element($0).scope()”

4) You will see the scope details for the element.

So I’m on my grandmother’s wifi network. I want to connect my iPad but she can’t find the password. My Macbook is connected to the network already so how can use it to find password for the network?

1) Search for Keychain Access

2) Look for the wifi network. For me, I found it by clicking on “Local Items” and “Passwords” (it’s Cute Kittens)

3) Double click on the desired network to bring up a window

4) Click on the “Show password:” checkbox, enter your laptop’s admin password and you will see the password of the network.

This morning when I ran our normal gulp task to build I got the following error:

09:09:12] 'watch:prod' errored after 372 ms [09:09:12] Error: EMFILE: Too many opened files.    at Gaze._handleError (/Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/gaze.js:436:31)    at Gaze._watchDir (/Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/gaze.js:302:17)    at /Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/gaze.js:358:10    at iterate (/Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/helper.js:52:5)    at /Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/helper.js:61:11    at /Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/gaze.js:420:5    at iterate (/Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/helper.js:52:5)    at /Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/helper.js:61:11    at /Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/gaze.js:420:5    at iterate (/Users/por364/Projects/ngad/node_modules/gulp/node_modules/vinyl-fs/node_modules/glob-watcher/node_modules/gaze/lib/helper.js:52:5)

The solution is to check

por364$ ulimit -n 256

then set it to a higher value

por364$ ulimit -n 1048

When learning the fundamentals of computer science in school, I found myself failing to grasp the significance of certain concepts. Consider the subject of multi-threading and the dangers of race conditions. A race condition is a situation where a program (or thread) depends on the timing or sequence of another program. I understood it enough to regurgitate the definition for the exam. It was one of those things that wouldn’t really stick unless I experienced it in the “real world.” Recently, I had just that experience.

I am allergic to nuts (and peanuts). Deathly allergic, in fact. Naturally with such a dietary restriction, I do what I can to avoid them: I ask if what I order has nuts, I carry an Epi-Pen (just in case), and I usually abstain from deserts. Unfortunately, I do ingest them from time to time.

I went with my fiancée to Ivanna Cone, the best ice cream shop in Lincoln, NE. If you ask, they give little sample spoons of their flavours. My fiancée asked to try two, “may I please try Ginger Panna Cotta and the Honey Almond?” “Certainly,” answered the ice cream maker, grabbing a spoon to scoop the first flavor out, Ginger Panna Cotta. As my fiancée tasted the first flavor, I thought it would be a reasonable time to submit my request for Vanilla Ice. The woman handed me a spoon of frozen delicatessen. I savored the sweetness and felt the texture of the ice. Meanwhile, my fiancée handed her spoon back and received her second spoon. Can you identify the race condition? Let me try to describe it a little better.

My fiancée requested two flavors: Ginger Panna Cotta and Honey Almond.

The woman received the request. The two flavors were stored in memory. She provided the first sample, Ginger Panna Cotta. The Honey Almond stayed in memory while she waited for my fiancée to finish.

I requested Vanilla Ice.

The woman accepted the request. The flavor went into memory, after Honey Almond. Instead of waiting to give my fiancée her flavor, the woman provided me with the next spoon: Honey Almond.

My fiancée finishes her spoon and receives the next spoon, Vanilla Ice.

The texture I felt was not ice but almond. I quickly grabbed a napkin and discretely spit out the nuts. Fortunately, this happened quickly enough (and I ate slowly enough) that only my lips were allergized. What could’ve been a really uncomfortable afternoon at the hospital turned out to be a learning lesson.

What could the woman have done to prevent this from happening? Now, don’t get me wrong, I am not saying she is to blame: I should’ve waited my turn and my fiancée probably should’ve abstained from Honey Almond while I was around. But, for the sake of discussion, let’s say the woman is a Java program and patrons are threads. After all, a software developer can’t assume a user will wait to submit another request.

The woman could use a mutex, or a mutual-exclusion semaphore. A mutex allows for one thread to access a block of code at a time. In the ice cream example, my fiancée submitted two requests. She acquires the lock on the block of code that fulfills requests. If I tried to submit a request, I would have to wait until she releases the lock. Consider the following code:

public class Synch {

    public static void main(String args[]){

        IceCreamMaker woman = new IceCreamMaker();

                Caller fiancee = new Caller(woman, "Ginger Panna Cotta");

        Caller fiancee2 = new Caller(woman, "Honey Almond");

        Caller me = new Caller(woman, "Vanilla Ice");

                //wait for thread to end

        try {

            fiancee.t.join();

            fiancee2.t.join();

            me.t.join();

        } catch (InterruptedException e){

            System.out.println("Interrupted");

        }

    }

}

class Caller implements Runnable {

    String flavor;

    IceCreamMaker target;

    Thread t;  

    public Caller(IceCreamMaker targ, String s){

        target = targ;

        flavor = s;

        t = new Thread(this);

        t.start();

    }

        public void run(){

//        synchronized(target) {

        try{

            Thread.sleep(1000);

            target.call(flavor);

        } catch (InterruptedException e){

            System.out.println("Interrupted");

        }

//        }

    }

}

class IceCreamMaker {

    void call(String msg){

        System.out.print("[" + msg);

        System.out.print("]");

        try {

            Thread.sleep(1000);

        } catch (InterruptedException e) {

            System.out.println("Interrupted");

        }

    }

}

Note that I commented out the synchronized block. When this program runs, the output could be any order of the flavors, including the dreaded [Ginger Panna Cotta][Honey Almond][Vanilla Ice]. If we uncomment the synchronized section the output is the safe and desired-well, actually not quite. Even though Caller will be safe from interruption, we still have to worry about the order of the requests.

Now, I must be honest. I spent longer than I wish to say playing with the above code. I wanted to recreate the real life situation in a simple java code but I couldn’t quite do it. Part of the problem was the decision to use fiancee2.t.join() Joining a thread to another one, on some level, dictates the order of the threads. fiancee2 will wait for fiancee to finish. Maybe I could wait() to somehow to recreate the Ivanna Code situation but I feel like that is a little contrived. I would be forcing the threads to go out of order but in a particular way so it wouldn’t really replicate the race condition.

This article was an attempt to describe how important computer science concepts, namely multithreading, may surface in the unexpected ways and places. Thanks for reading!

I have a scanner and, from time to time, I scan book pages to read on my iPad or computer.

So once I have a set of images, I convert them to a pdf. Unfortunately, the pdf is too large. What do I do?

I would like to compress it but I don't have a copy of Adobe Acrobat Reader X and I don't want to buy a license.

There are a slew of "Free PDF optimizer" sites but, more often than not, they are 1) not actually free and 2) the "free" compression method puts a watermark on the final pdf.

That's no good.

Hello! It has been forever and a day since I updated this blog and for that I apologize.

In any case, I am going to be learning the statistics programming language R and will be making posts with little tips and tricks that I have found.

Looking for movies or song in Windows Explorer, for me, is always marked by the frustrating file information pop ups which appear after a few seconds of hovering over a particular file. It interrupts be from fully reading what I want to read and it doesn't provide any useful information: last modification date and file size. Here is an example:

I had forgotten how to stop it until irritation overcame apathy and I looked for the surprisingly easy solution. Note, these pictures are on my Windows 8 machine, but the instructions with work with other versions of Windows despite the differences in User Interface (or slightly different phrasing).

In a Windows Explorer window, click "View" in the top left of the window, in the toolbar.

Next, click "Options" and the "Folder Options" window will appear.

Now, click on the "View" tab.

In the long list of "Advanced settings:",

click the check-box next to "Show pop-up description for folder and desktop items".