Thursday, August 4, 2011

Create a Perl Module Skeleton Using h2xs

The h2xs binary is used to convert C header files to Perl extensions, but it can also be used to create a Perl module template. Creating modules this way will save you a lot of time and make sure that your module is setup up correctly for submission to CPAN.

You can create your own module skeleton with h2xs using:

h2xs -A -X -n My::Module

This will create a directory called My-Module with the following files:

My-Module/MANIFEST is your actual module, which you will edit and add your desired functionality into. Your module can be installed on your system by following these steps:

perl Makefile.PL

This creates the makefile

make test

This executes all tests, assuming you have created some.

make install

This will install the module in your system, you may have to execute this line as super user.

You can package up your module for submission to CPAN, or other distribution means by typing:

make tardist

This will create My-Module-0.01.tar.gz inside your project directory.

Wednesday, July 27, 2011

Convert YouTube Videos to MP3

I often find songs on YouTube that I can't obtain elsewhere, especially obscure remixes of popular songs. While it is possible to listen to them directly on YouTube this gets tiresome quickly since you can't add the songs into a GrooveShark or iTunes playlist or play them on your iPod.
I've used several services online that will convert a YouTube video to MP3 format and allow you to download it. These services are covered in banner ads, encode MP3s in low quality and frequently don't work at all.
While browsing, I discovered a free program called "YouTube to MP3", it's completely free and allows you to extract only the audio from a YouTube video. This program allows you to select the bitrate, and format. You select the YouTube video you want to download by either clicking the paste from clipboard button or manually typing the URL in. Another nice feature this program has is downloading several songs at the same time.

The program runs on Mac and Windows and can be downloaded from here:

Friday, July 8, 2011

Backup a MySQL Database Nightly

I run several websites, which use MySQL, and I've discovered the importance of backing up my databases regularly. I've had tables become corrupt, and hard drives go without warning. It's important to have a backup plan so you can restore your website quickly if something goes wrong.

The easiest way to backup a MySQL database is to use the mysqldump program, which is included with MySQL server. The mysqldump program allows you to dump a database or table to an SQL file which can be quickly restored using the MySQL command line client. You can ensure your backup is executed on a regular basis using the crontab.

Here is a sample shell script for backing up a MySQL database:


DATE=`date +%Y-%m-%d`
cd /PATH_TO_BACKUP/db_backup
mkdir $DATE
/usr/local/mysql/bin/mysqldump -u root DATABASENAME > /PATH_TO_BACKUP/db_backup/$DATE/DATABASENAME.sql

The first line stores the current date as a string of the form YYYY-MM-DD, the next two lines change to the directory where you want the backup to be stored and creates a folder named the current date. The next line creates the actual backup using mysqldump, using the root@localhost account. The final line compresses the backup using the gzip utility, this is optional, but it is a good idea if you have a large database.

You can add this script to your crontab and have it execute daily by first typing:

sudo crontab -e

Then adding the following line into your crontab:

1 0 * * * sh /PATH_TO_BACKUP_SCRIPT/

This will execute the script at one minute past midnight every night, but you can easily change this to suit your needs.

We can easily restore from our backup in a few easy steps. First open Terminal and navigate to the folder where our backup is stored. Then type:

gunzip -c DATABASENAME.sql.gz | mysql -u root DATABASENAME

This will decompress our backup, recreate the table structure and import all the data that was stored in the tables. Make sure you have created the database in MySQL prior attempting to restore.

Wednesday, June 29, 2011

Change Your Bash Prompt

The Bash command prompt can easily be changed by modifying the value of the PS1 environment variable. For example: PS1='yes master?> ' will change your command prompt in terminal to "yes master?> ". If you want your command prompt change to become permanent add it to your .bash_profile or .profile file in your home directory.

In addition to changing your bash profile to a simple string of text there are a number of special characters that can be used. The special characters can be used to add things like the current working directory or the current time to your prompt. Below is a list of these special characters taken from the bash manual:

\a A bell character.
\d The date, in "Weekday Month Date" format (e.g., "Tue May 26").
\D{format} The format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results in a locale-specific time representation. The braces are required.
\e An escape character.
\h The hostname, up to the first `.'.
\H The hostname.
\j The number of jobs currently managed by the shell.
\l The basename of the shell's terminal device name.
\n A newline.
\r A carriage return.
\s The name of the shell, the basename of $0 (the portion following the final slash).
\t The time, in 24-hour HH:MM:SS format.
\T The time, in 12-hour HH:MM:SS format.
\@ The time, in 12-hour am/pm format.
\A The time, in 24-hour HH:MM format.
\u The username of the current user.
\v The version of Bash (e.g., 2.00)
\V The release of Bash, version + patchlevel (e.g., 2.00.0)
\w The current working directory, with $HOME abbreviated with a tilde (uses the $PROMPT_DIRTRIM variable).
\W The basename of $PWD, with $HOME abbreviated with a tilde.
\! The history number of this command.
\# The command number of this command.
\$ If the effective uid is 0, #, otherwise $.
\nnn The character whose ASCII code is the octal value nnn.
\\ A backslash.
\[ Begin a sequence of non-printing characters. This could be used to embed a terminal control sequence into the prompt.
\] End a sequence of non-printing characters.

Friday, June 24, 2011

Fun With Speech Synthesis

This is a fun way to freak out anyone around a remote Mac using SSH and the builtin text to speech libraries in OS X. The idea is to SSH into a remote Mac and execute the say command, which will convert a string of text into speech. You can use this to "talk" to people around your remote Mac. For example:

say -v "Zarvox" "hello world"

Will speak the phrase "hello world", using the voice Zarvox. If you don't specify a voice the default from the System Preferences will be used. Here is a list of other voices you can use:

Bad News
Good News
Pipe Organ

On the off chance that the Mac you are attempting to have speak has its volume turned down or is muted, you can also turn the volume up using the following command:

sudo osascript -e "set Volume 10"

This will set the system volume to maximum to ensure that any bystanders can hear your Mac speak. Setting the volume does however require the root password.

Monday, June 13, 2011

Programmatically Calculate Battery Charge

This is a cool way to determine what the charge of your battery is on a Mac laptop using Perl. Basically we execute the command ioreg -l in a shell and filter out all the results except MaxCapacity and CurrentCapacity, then we use regular expressions to parse out just the values. From there it's just a matter of calculating what percentage current capacity is of the max capacity and printing out the results.

#!/usr/bin/perl -w

my $MaxCapacity = `ioreg -l | grep 'MaxCapacity'`;
my $CurrentCapacity = `ioreg -l | grep 'CurrentCapacity'`;

$MaxCapacity =~ /(\d+)/;
$MaxCapacity = $1;

$CurrentCapacity =~ /(\d+)/;
$CurrentCapacity = $1;

printf("Battery Charge: %d %%" . "\n", (($CurrentCapacity / $MaxCapacity) * 100));

Executing the script produces something similar to:

Battery Charge: 90 %

If you execute this on a Mac that doesn't have a battery you will probably get a division by zero error.

Friday, June 10, 2011

Shorten a URL on using CURL

I often have to shorten URLs when I'm tweeting or simply sending a URL to a friend via email or on instant messenger. Since I generally have a terminal window open I figured it would be expeditious to come up with a shell script to do this for me.

The first thing you have to do is sign up for an account on if you haven't already, next you have to obtain an API key. You can sign up for a account at: if you already have an account you can get your API key at:

First create a shell script called


curl -s "$1&format=txt" | pbcopy

This script uses curl in silent mode to connect to the API and shorten the url specified by longUrl. Since we want to shorten a variety of URLs I've used $1, which refers to the first argument the script was invoked with. You'll also notice the format parameter, this can be set to xml, json or txt, we're using txt so we don't have to do any parsing. We are piping the output of our curl command into pbcopy a command line utility provided by OS X which provides copying to the clipboard. Pbcopy basically copies all output it receives into the clipboard.

Make sure to fill in YOURLOGIN with your login and YOURAPIKEY with your API key. Save the shell script somewhere it's not going to be deleted by accident or moved. If you use bash open your .bash_profile file in your home directory. You may have to create it if you haven't made any changes to it before. Add the following line:

alias shorten='/bin/bash /PATHTOSCRIPT/'

Where PATHTOSCRIPT is the path to where you have stored your script. This alias will allow us to invoke our script from anywhere using "shorten" instead of the full path to the script. In order for your .bash_profile to be reloaded and the alias to become active, you need to either type source .bash_profile or open a new terminal window.

Now when you type:

shorten YOURURL

Where YOURURL is any URL you wish to shorten, the shortened version will be copied directly into your machine's clipboard.

Tuesday, June 7, 2011

Analytics For iOS Developers

I have a couple of iPhone apps in the App Store and I was getting quite frustrated with having to haul out a calculator every time I wanted to figure out how many downloads each of my Apps have in total. iTunes Connect seems to be very limited in the data it displays to developers and also how long that data is retained for.

Enter App Figures, a service that syncs with your iTunes connect account daily, and downloads and stores the data. In addition to storing updates, downloads, ranking, and reviews for each app in your account, it also stores iAd statistics. The data is presented in a really nice format with lots of graphs, it is quite reminiscent of Google Analytics.

If you're looking for a better way to keep track of your App Store apps check out You can try out the service for free, and once the trial period is up it only costs $4.99 a month and includes tracking of 2 apps.

Friday, June 3, 2011

Five Mac OS X Apps I Can't Live Without


Jumpcut remembers all of the text you've copied to the clipboard up to a hard limit that you specify. It provides a menu on the menu bar that shows you all the text you have copied to the clipboard. Everything is saved so text you have copied persists even after you restart your Mac.

In addition you can set a hot key, which shows a bezel, that can be used to scroll through all the items stored in Jumpcut. This can save you going back and forth to the menu item and once you get used to it can save you a lot of time.

I find this utility incredibly useful, as it allows me to copy several items and paste them one after another without having to go back and forth. I also constantly find myself needing items again after I've already copied something new into the clipboard.

The only caveat of this utility is it manipulates the clipboard using Command + V programmtically, which means it may not work properly in any application that uses a different key combination for pasting.

Jumpcut is free of charge and completely open source.


Quicksilver is an awesome utility that allows you to do just about anything on your Mac with a couple keystrokes. Quicksilver takes a little getting used to but once you're acclimatized to it, it's difficult to live without.

Quicksilver indexes your hard drive, similar to spotlight and the UNIX locate utility. Quicksilver runs in the background and is activated with a keyboard shortcut you specify. Once Quicksilver is activated you can just start typing the name of a file or application and Quicksilver searches it's catalog and attempts to find it. From there you can open the file by pressing enter or you can type actions to be done to the file, like moving, and deleting. This is really just scratching the surface of what Quicksilver is capable of.

The bottom line is Quicksilver will make you more productive, by allowing you to manipulate files and applications in fewer keystrokes.

Quicksilver is freeware.


Adium is a multi protocol instant messaging application. It allows you to add all your instant messaging accounts into one application. Adium displays one contact list and allows you to communicate with all your contacts as if they were all in the same account.

Adium supports: AIM, Jabber, MSN, Yahoo, Facebook, Google Talk and many more protocols. It also provides logging of chat transcripts and the ability to connect through a proxy server.

I occasionally switch back to iChat because it allows me to to do video chat over my AIM account, which I sometimes need for work. The Adium team is working on adding Audio and Video in the future.

Adium is free of charge and completely open source.


BBEdit is a text editor designed for Web and Software developers. It provides a rich toolset while still being easy to use and lightweight.

BBEdit includes syntax colouring for pretty well every programming language you can imagine and also features autocompletion. It provides support for version control using CVS and SVN. One of my favorite features is the ability to open files over FTP and SFTP, this allows you to edit remote files as if they were local. BBEdit is also great for maniuplating text, it allows you to use grep regular expressions for find and replace operations.

If you need a powerful text editor BBEdit is the way to go; Bare Bones Software, the people who make BBEdit, also provide a free version of BBEdit called Text Wrangler which has a lot of the features of BBEdit.

BBEdit costs $99.99 dollars for an individual, but they also have educational pricing which is about half the cost.


GeekTool is a cool System Preferences module that allows you to anchor the output of any shell command to your desktop. You can also monitor files like /var/log/system.log, and the image module lets you display the output of programs like MRTG, which generates server performance graphs dynamically.

With GeekTool you can see how much uptime your machine has or how much disk space is left on your drives without opening up a Terminal window. You can set how often the shell commands are executed and configure how they're displayed inlcluding font and colour. GeekTool shows up in your system preferences as it's own pane.

Geek Tool is free of charge and completely open source.

Thursday, June 2, 2011

Change Terminal Title With Bash

Programmatically change the title of the active Terminal window from the Bash Shell. This can be useful for a variety of things, I like to alias the names of the servers I connect to in SSH to simply the server's name. I also change the title of the Terminal window in the alias so I can keep track of which terminal window is connected to what server. If you open multiple tabs in Terminal the window title will also appear in the tab.

Changing the Terminal window is very straight forward simply type: echo -n -e "\033]0;WINDOW_TITLE\007" where WINDOW_TITLE is the string you want the title of the window to be. Changing the window title isn't permanent, and you can execute the command several times and only the most recent change will be reflected.

It is also possible to put variables into the window title, for example: echo -n -e "\033]0;$HOSTNAME\007" will change the title of the window to the name of the current host.

Wednesday, June 1, 2011

Surf Through a Proxy

Surf anonymously through an SSH tunnel to your home computer. This requires you have access to a remote computer with port 22 open and SSH server installed (should be installed by default on OS X, just enable remote login in the sharing panel).

For best results you should also use Firefox because it allows you to specify whether or not DNS lookup is done on the client or server side. If you use Safari or Chrome you the websites you visit will be obscured, but the local DNS server will still be used to look up addresses and it could reveal what websites you are visiting.

To start the proxy open a terminal window and type "ssh -ND 8080 <username>@<yourremotemac>" on the machine you want to surf anonymously on, where <username> is an account on your remote machine and <yourremotemac> is the IP address of your remote computer. This will start a SOCKS proxy on your remote machine and port forward all traffic on port 8080 on your local machine to the proxy. Because the proxy operates through SSH all traffic is encrypted and will not be interceptable by a third party. I'm using port 8080 but you can use whatever port you want as long as it's not in use by another service.

Next we have to configure Firefox to connect to the internet through a proxy. Open Firefox and select Preferences under the file menu, then select the Advanced tab and click the settings button next to where it says connection. The image below shows you how to configure the dialog box that appears.

Now Firefox needs to be configured to use remote DNS lookup. Type "about:config" into the address bar, you will get a warning dialog about voiding your warranty, click the "I'll be careful I, promise" button. Type DNS into the filter box or scroll down to the entry for "network.proxy.socks_remote_dns" and set the value to true. Firefox should now be connecting to websites through your proxy server. You can double check everything is working properly by navigating to a site like and ensuring the IP reported is that of your remote machine and not your local machine.

Tuesday, May 31, 2011

Pull Twitter Trending Topics using Perl

This is useful for a wide variety of applications and it doesn't require you to sign up for an API key. The only limitation is Twitter only allows you to pull this information 150 times an hour. Other Twitter API calls may affect this limit as well.


use strict;
use warnings;
use JSON;

my $curl_string = `curl -s`;

my $json_result = from_json($curl_string);

foreach my $trend (@{$json_result->[0]->{'trends'}}) {
    print $trend->{'name'} . "\n";

This script requires that you install the Perl JSON module by Makamaka Hannyaharamitu. This can easily be done either by downloading and compiling it from or by running the cpan command line interface and typing "install JSON".

I'm also using the curl binary to execute the request by executing a system call from inside Perl. You can also use the perl bindings for libcurl to execute the request.