Monthly Archives: February 2013

qmail log files on Plesk CentOS server

After a big of digging around on a server today, I followed my nose to where the log files are held.

qmail is started from within /etc/init.d/qmail. Searching for qmail-start reveals two ways in which qmail can be started, the Debian way or the “other” way. As this is CentOS we need the “other” way, which is:

qmail-start "$defauldelivery" splogger qmail &

The splogger argument tells qmail to use the syslog for logging, and CentOS uses rsyslog so look in the file /etc/rsyslog.conf. There you will find the line:

mail.*                    -/usr/local/psa/var/log/maillog

which finally leads us to the path to the qmail log file:

/usr/local/psa/var/log/maillog

Phew, got there at last! 🙂

‘mod_alias’ and ‘mod_rewrite’

I spent a few hours recently trying to debug some Apache Rewrite rules on our development server.

We had a particular directory outside the root of the website that I was using an Alias command to make available. However, within this directory I also wanted to apply a couple of different Rewrite rules.

A simple cachebuster

One of the rules was basically to remove instances of the string nocache_XXXX_ where XXXX was a number which could change (this is usually a date-stamp, such as 20130131 if modified on 31st Jan, 2013). This allows us to easily change the number in the URL which will force the browser to reload the page, avoiding possible caching problems.

For example:
http://www.example.com/nocache_20130131_js/file.js
will be rewritten as
http://www.example.com/js/file.js
If the file.js changes we can modify the number in the url, which will force the browser to load the JavaScript again as it is a different URL, but the web server will return the current “file.js” inside the “js” directory, after the rewrite rule has been applied.

To cut a long story short, I found out that mod_alias and mod_rewrite cannot be used together. Therefore, the workaround in my case was to use just mod_rewrite and use a symbolic link instead of trying to use mod_alias. Note that to allow symlinks to be use, it is also necessary to specify Options FollowSymLinks within the Apache config for that site.

Maybe this will help someone else avoid wasting time trying to get mod_rewrite to work on top of mod_alias.

Executable PHP files

I have a PHP script that I will be running in one of three ways:

  • interactively, from the Linux command line
  • as a cron tab, on a Linux box
  • as a web page, with Apache and mod_php

In order to do this I found that I can do the following:

#!/usr/bin/php -q
<?php 
@ob_end_clean();

if (isset($argv)) {
	define("SHELL",true);

	$options = getopt("c");
	if (isset($options['c'])) {
		echo "Running as a cron job ...\n";
		define("INTERACTIVE",false);
	} else {
		echo "Running interactively ...\n";
		define("INTERACTIVE",true);
	}

} else {
	echo "Running via Apache...
";
	define("INTERACTIVE",false);
	define("SHELL",false);
}

The general idea is:

  1. Line 1: tell the Linux shell that the command, when executed directly, should be interpreted by php, and not the shell that you’re running in (“-q” tells PHP to suppress any HTTP headers).
  2. Line 3. If the script is running via Apache then tell it to remove the first line which has already been output. Use the @ to suppress warnings as ob_end_clean isn’t available when running from the CLI.
  3. Use the $argv array to determine if we are running via CLI, it’s not set when run through mod_php
  4. When executed from cron, we will pass a parameter “-c” to indicate it should run in “non-interactive” mode, use getopt to read the parameters and isset to check if the “-c” parameter was passed.
  5. Now, the SHELL and INTERACTIVE constants can be used to determine if we are in a shell or Apache, and interactive or cron-mode, respectively.

Finally, don’t forget to chmod the script to make it executable.

chmod 700 script.php

Skype command line switches

There are a few Skype command line switches documented on the Skype support site:
https://support.skype.com/en/faq/FA171/can-i-run-skype-for-windows-desktop-from-the-command-line

However, it seems that the list isn’t complete. From a post on the Skype community site (the post doesn’t seem to be available any more) I found the following additions:

This will start Skype with the specified account name and password:
"C:\Program Files\Skype\Phone\Skype.exe" /username:your user name /password:your password

This will start a “portable” Skype installed at “path to skype.exe” with all data being saved in the “Data” folder:
"path to skype.exe\Skype.exe" /datapath:”Data” /removable