Mime information using file command

A way to get mime type is by running this command

$ file -bi filename

The problem with this approach is that it gave me different results on gentoo and debian. Ofcourse the file executable version were different (4.16 and 4.23) but I still feel this approach is not very robust.

Using ruby libraries to find out audio file information

Another approach is to use a ruby library to check for file type. However the issue is that there is no single library that can check for different kinds of files. The only way I have been able to figure out is to try and open the files in different libraries (and catching exceptions). I found a list of popular ruby audio libraries here.

In fact on searching some more, I found a similar approach being followed in metadata extractor library too.

def sanitize_filename(filename)
  returning filename.strip do |name|
    # NOTE: File.basename doesn't work right with Windows paths on Unix
    # get only the filename, not the whole path
    name.gsub! /^.*(\\|\/)/, ''

    # Finally, replace all non alphanumeric, underscore or periods with underscore
    name.gsub! /[^\w\.\-]/, ‘_’
  end
end

The shortcut \w is described here as letter or digit; same as [0-9A-Za-z]. However since ruby regex engine has support for unicode, letter means any unicode character. So it will let characters like 爱与希望 remain. This can be a problem if you are passing a filename containing such characters to a flash player. The flash player just won’t play the file!

A quick solution would be to check specifically for 0-9A-Za-z. This can be done by changing the function to

def sanitize_filename(filename)
  returning filename.strip do |name|
   # NOTE: File.basename doesn't work right with Windows paths on Unix
   # get only the filename, not the whole path
   name.gsub! /^.*(\\|\/)/, ''

   # Finally, replace all non alphanumeric, underscore or periods with underscore
   #            name.gsub! /[^\w\.\-]/, ‘_’
   #            Basically strip out the non-ascii alphabets too and replace with x. You don’t want all _ 
    name.gsub!(/[^0-9A-Za-z.\-]/, ‘x’)
  end
end

Finally this is not a problem if non ascii characters don’t cause any issue in your site.

Services like dyndns are quite stable and allow you to setup 20s timeout on DNS which is useful in case your site goes down and you need to switch servers or something. This comes in very handy if you are running your site off a single server and need to switch to blog or something in case the server goes down.

How to Setup the DNS using DynDNS

First of all you need to buy an account with dyndns.com. You need to buy a custom DNS hosting account. Once you have done that you need to point the DNS on your registrar’s DNS panel (where you have booked the domain) to dyndns name servers. So this will make sure that all the DNS queries for yourdomain will come to the DynDNS name servers (this is just like pointing to your hosting company’s name server and they doing the job for you)

Next step is to setup the A record for yourdomain to the IP address of your webserver (VPS in this case). You can also create several other subdomains and point them to your webserver. You can also point the MX servers to your mail servers (or google apps if you use that). DynDNS also supports redirecting a domain or subdomain to another url so you can use that to setup useful aliases.

So this is how things will look in the end. For this example I am assuming that you booked your domain on GoDaddy.com, got a DNS account at DynDNS.com and your website is hosted on a VPS on vpsfarm.com

User types yourdomain.com —> DNS server is resolved to DynDNS.com and DynDNS returns that the A record for yourdomain.com points to vps1 (say 209.178.xxx.yyy) —> Apache on 209.178.xxx.yyy gets the request and serves the webpage.

I know that this tutorial does not explain everything step by step but I think this should give you enough pointers to setup your DNS using DynDNS

Also as a last point, there are some free alternatives to DynDNS too. I have personally used freedns.afraid.org

The setting can be increased by simply changing the variable srvtimeout to a larger number (say 120000 for 120 secs) in the configuration file /etc/rails/haproxy.conf

If you are specifying the aws access key and secret key in the s3config.yml file you need to make a small change in s3config.rb file. In s3config.rb you need to change the confpath variable to

confpath = ["./", "#{ENV['S3CONF']}”, “#{ENV['HOME']}/.s3conf”, “/etc/s3conf”]

This makes sure that s3config.rb picks up the config file from same directory too. Once you make this change, s3cmd.rb and s3sync.rb should start working fine. After that you can use it pretty much like rsync and schedule it with cron. If you don’t want to load your cpu too much use the –no-md5 option (check the readme file in the package)

Do keep a watch on your s3 bill though .. everytime you try to sync, fetching the list of files etc also costs some money.

From

    :path_info => '/files/upload‘, 

To

    :path_info => ['/files/reupload','/files/upload'],

With this modification, once you restart your mongrel it will start watching for uploads on /files/reupload too. However there is a small gotcha to lookout for if you are submitting your form to a url that looks like

/files/reupload/song_id

This won’t work because mongrel will be watching out for /files/reupload and not /files/reupload/
If you look at the plugin code, it does the following to check whether it has to watchout for this action or not

return unless @path_info.include?(params['PATH_INFO']) &&
        params[Mongrel::Const::REQUEST_METHOD] == ‘POST’ &&
        upload_id = Mongrel::HttpRequest.query_parse(params['QUERY_STRING'])['upload_id']

where @path_info is an array created for :path_info line of the config file. Since the plugin checks for the exact path and not a regular expression even a trailing / can screw things up.

I spent almost a day in figuring this out. Hope this post saves you sometime.

I did some googling around and found that I have to setup mysql (atleast when I install using gentoo ..ie from source). I tried to install it with the commant

<code>#emerge –config =dev-db/mysql-5.0.54</code>

However this would still not let me login because of some bug in mysql that has been reported here and officially here

I therefore changed my hostname to something other than localhost as described in the forum but still i could not connect as root. I finally looked at mysql_install_db help and found out that there is a way to skip name resolution and tried with that

<code>

#mysql_install_db –user=mysql –skip-name-resolve

#/usr/bin/mysqladmin -u root password ‘new_password’

</code>

Voila .. it worked and i could login as root. I hope this is useful to someone

I spent the whole day today installing gentoo the good old command line way and finally have been able to get the basic system, sounds and XFCE up. I am currently installing all work related stuff (ror, java etc) and I think by tomorrow I should be back in the game. Speed looks good so far and I know that gentoo should not let me down. I will post a detailed review sometime later

I code mostly in ruby on rails and sometime work with openlaszlo to create flash widgets. I have some open source code in openlaszlo to document and release. Therefore I plan to continue writing about my technical learnings in this blog and also release some code every now and then in public domain.

Over the next few days, I will burn this feed, get a better template and move some of my technical posts from my other blog here.

Happy Startup Coding till then!