Posts Tagged ‘Hacks’

Interactive file merging with Unison

August 13th, 2009 3 comments

After trying in vein to find decent documentation on the Merge functionality of Unison I eventually gave in and invested an hour or two trying out different Linux based merge programs in order to find something Unison, the merge program and I were happy with.

So onto the diff-merging candidates:

VimDiff (part of Vim)

Doesn’t work too well with Unison. I can’t get gnome-terminal (my terminal of choice) to execute synchronously so I was forced to fall back on XTerm instead.

After using XTerm I immediately hit upon a problem: there is no sensible way of outputting the results of a merge in VimDiff. Which is a pity because I do prefer VIM as an editor but this lack of functionality is annoying (yes I could have used a wrapper script but I’m trying to keep this simple).


Very pretty but lacks features such as ‘Use Left-hand-side-file for all changes’ and some of the other filtering options provided by KDiff3.

Also, like, VimDiff, does not provide any sensible output mechanism of the eventually merged file.


Not as good looking as Meld but provides pretty much everything I want in a merge program including the all important merged file output that Unison requires.

Can get a little annoying though with its insentient pop-up boxes. I wish there were a ‘Dont show this option again’ option to each. KDE is usually quite good with this so I’m not sure why KDiff3 managed to escape this unspoken standard.


So how to use KDiff3 with Unison? First install kdiff3:

apt-get install kidff3

Then open your Unison profiles .prf file and insert the following:

merge = Name * -> kdiff3 CURRENT1 CURRENT2 -L1 'Local File' -L2 'Remote File' -o NEW -m
confirmmerge = true

If you are comfortable with KDiff3 you could remove the ‘confirmmerge’ line which forces Unison to double check you actually want to accept the changes.

The downside to the above interactive merging process is there is no sensible way to preview the merge in Unison (the ‘View Merge’ button in the confirmation dialogue). For now though its preferable to not having this functionality at all.

Categories: HowTo's Tags: , ,

Converting Null

April 24th, 2009 2 comments

Simple shell script fix this week – convert all newlines to null characters.

Since most Linux shells have a major problem with doing this in a sensible way, the following (on my box called simply ‘0’) takes any input (either from files or via a pipe) and converts the characters.

# From:
# Author: Matt Carter 
while (<>) {

So now commands like:

find -type f | 0 | xargs -0 | mplayer

work perfectly (in the above case to play all files in directories recursively.

You may well ask why I don’t use the simple ‘-print0’ argument for the find program – because it doesn’t work when using later pipes.

For example if i wanted to sort the above, ‘sort’ would see the null symbol as a regular character.

So ‘0’ works nicely in this case:

find -type f | 0 | sort | xargs -0 | mplayer

Or even:

find -type f | 0 | shuffle | xargs -0 | mplayer

To play all files recursively, in random order. See the article on shuffle for the source code of that filter.

Categories: Fixes, HowTo's Tags: , , ,

Easy Apache VirtualHost config

March 15th, 2009 1 comment

Like most of the word I use Apache to serve up both my live and test websites.

The downside to having a box for development though is the constant config of apache to host these sites, most of which require absolute links (e.g. ‘/css/style.css’) to function.

The Apache snippet below sets up dynamic sub-domains which can be changed without reloading Apache every time you add, remove or update anything something. Simply drop your sites inside /var/www whenever you want a new subdomain. Alternatively you can symlink if they are hosted elsewhere on the box.

Its pretty easy to install, simply paste the below in your /etc/apache2/apache.conf file…

# Easy virtual host config
# See

DocumentRoot /var/www/
ServerAdmin admin@localhost
Options +FollowSymLinks -Indexes
LogLevel debug
ServerAlias localhost
ServerName localhost
RewriteEngine  on
RewriteLogLevel 3
RewriteCond    %{HTTP_HOST}  ^localhost
RewriteRule    ^(.*)$        /www/$1 [L]
RewriteCond    %{HTTP_HOST}  ^www.*
RewriteRule    ^(.*)$        /www/$1 [L]
RewriteCond    %{HTTP_HOST}  ^(.*)\.localhost
RewriteRule    ^(.*)$        /%1/$1 [L]

Now add your servers to the /etc/hosts file:      server.localhost

Now any directory you place in the /var/www directory automatically becomes a subdomain. You can now visit http:///server.localhost as a fully fledged webhost.

If you want to use another name than the rather boring ‘localhost’ simply replace the text in both text pastes above.

If only there were a way of removing that /etc/hosts hack it would mean zero config from then on. If anyone has any ideas do let me know. The addition to the hosts file seems to need applying if you are working from the same box the Apache server resides on. If you arn’t and the box is a local dedicated server its not needed at all and domains can be added and removed as necessary.

Categories: HowTo's Tags: , ,

Talking in tongues – UTF8 with CodeIgniter

February 16th, 2009 14 comments

PHP 4 & 5 unfortunately have major problems working with UTF8. Hopefully this will be solved with PHP6 and its fancy pants new rendering interface.

Until then we have to make do and mend.

First setup your database to work with UTF8. I won’t waste time telling you how to do this in MySQL as many people far brighter than I have written more on the subject.

CodeIgniter comes with UTF8 enabled out of the box so there is little to do configuration wise. Unfortunately pasting a test string such as: 検索 (which I stole from this Wikipedia page) into a CI input box will quickly lead to calamity as CI tries to save the string as ASCII.

Simple solution then, save the following helper in your system/application/helpers folder:

* Info:
function ob_utf8($string) {
	return utf8_decode($string);

foreach ($_POST as $key => $val) // Re-write all incoming text into UTF8 streams
	$_POST[$key] = utf8_encode($val);

Then simply add it to your system/application/autoload.php:

$autoload['helper'] = array('utf8');

The helper will automatically convert incoming POST data into MySQL compatible UTF8 and convert outgoing text into HTML UTF8 streams.

Categories: PHP Tags: , , ,

Pretty URLS in CodeIgniter

January 12th, 2009 No comments

CodeIgniter has to be my favorite framework for PHP. The way it keeps out of your way while working to an MVC standard is something deserving of the highest praise.

For reasons passing understanding though the programmers of this excellent system have desided not to provide pretty URL’s out of the box. Getting infomation on this is a little tricky so here is my take on the situation.

Simply dump the following into a file called ‘.htaccess’ (Note the starting Dot) in the root path (thats the one at the very start of your path tree that should contain the ‘system’ folder).

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^(.*)$		- [L]

RewriteCond $1 !^(index\.php|images|robots\.txt)
RewriteRule ^(.*)$ /index.php/$1 [L]

As with most mod_rewrite hacks you will need that enabled on an apache server. Its very rare to find a hosting company that doesn’t use this setup so you should be fine.

You will also need to change the following variable to a blank value in the system/application/config/config.php file:

$config['index_page'] = '';

And you’re done. From now on your Urls are addressed in the form: http://SITE/CONTROLLER/METHOD/VALUE1/VALUE2 (e.g.

Categories: HowTo's, PHP Tags: , , ,