Linux diff Primer Tutorial
The Linux (or unix) command diff is a powerful command line tool that does file comparisons at the command line of a Linux (or unix) operating system. When you are coding this type of tool can be very important. You may not like to do such tasks in the command line, and have to say that a GUI (on Windows UltraEdit (text editor) is brilliant, on Mac think TextWrangler does a good job here) type of comparison works better for me, and Source Control techniques work well for many programmers, but GUI doesn’t always gel with integration, and want to show you today how the Linux diff can be incorporated into your PHP code. In saying this, am recommending extreme care with this, as its misuse can have bad implications for the whole website to be exposed to the outside world. Balancing this up against wanting to have a tool for users of this web blog to (have a more automated way to) be able to see the comparisons of files of changing code, as in yesterday’s tutorial, have decided to show the workings of this, in the rudimentary way it is used here. At the other end of diff, its output can be used by patch to make diff an even more powerful tool, and there are links about all this below.
Some good background reading here would be:
- diff (Linux or unix diff command)
- exec (as interface to use with PHP on the web)
- patch (as a way to use diff output as input to Linux or unix patch command)
So … why does the picture for this tutorial not show a Linux command line screen? Well, today we show you the power of the combination of Linux commands and the PHP way to access these commands (in our case with diff.php … the PHP exec() method). The follow up issue that tomorrow’s tutorial will address is the idea of an Apache web server configuration allowing a file “extension” to be mapped to a URL arrangement of your choosing … will save the idea here for that future tutorial, as this topic area is very big and needs the user to step back and think about, a lot, before considering.
Specifically, in diff.php (of the picture) it has a line of code …
exec(“diff ” . dirname(__FILE__) . “/one.one ” . dirname(__FILE__) . “/two.two > ” . dirname(__FILE__) . “/huh.huh”);
… to bring (Linux) diff results to the web for file comparison purposes … clicking on the picture of the tutorial shows a picture showing the link that got clicked to create the webpage of the front picture. This all sprung from yesterday’s PHP/Javascript/HTML Geographicals By Placename Tutorial. By the way, am not showing all the code of diff.php today, and am sorry about that, but rest assured the line of code above is its crucial part.
If this was interesting you may be interested in this too.
