Need to identify web crawlers and mobile devices with your web-app ? Here is the list of couple regular expressions you can use (most common values):
Mobile Devices:
/(blackberry|motorokr|motorola|sony|windows ce|240x320|176x220|palm|mobile|iphone|ipod|symbian|nokia|samsung|midp)/i
Web Spyders:
/(google|yahoo|baidu|bot|webalta|archiver|crawler|spyder)/i
Since i got trouble while connecting to wireless network with given parameters in linux, i tried a lot of ways to get my internet working.
So, the problem is: Windows Network manager have special option – Key index. The index is transmitted with the encrypted message. The receiver then looks-up the key corresponding to the transmitted index and uses it to decrypt the message. But linux (ubuntu) network managers i`ve tried have no key index field, so there is no way to set it up properly with gui. Connection won`t work if index value set to incorrect value.
After giving up to find any useful gui program i wrote small shell script only for one network (because i have no access to router and no chance to improve some security settings):
#!/bin/bash # settings interface="ath0" # wireless interface, default to wlan0 essid="NETWORK_NAME_HERE" key="YOUR_KEY_HERE" index="4" # can be [1..4] # check permission if [ "$(id -u)" != "0" ]; then echo "Run this script under root" 1>&2 exit 1 fi # show information echo "Settings:" echo "-> Interface: $interface" echo "-> Wifi ESSID: $essid" echo "-> Key: $key" echo "-> Key Index: $index" # perform association ifconfig $interface down iwconfig $interface essid $essid iwconfig $interface key $key [$index] iwconfig $interface key [$index] ifconfig $interface up dhclient $interface
Download shell script – http://files.sosedoff.com/9591756c/
For example, in your bash shell script you`re going to use some root-specific commands like network operations, mounting devices and so on. There are couple easy ways to check if your script is executing under root privileges.
#!/bin/bash # ... if [ "$(id -u)" != "0" ]; then echo "This script must be run as root" 1>&2 exit 1 fi # ...
Another way: use EUID. When user account created a user ID is assigned to each user. Bash shell stores the user ID in $UID variable. Your effective user ID is stored in $EUID variable.
#!/bin/bash # ... if [[ $EUID -ne 0 ]]; then echo "This script must be run as root" 1>&2 exit 1 fi # ...
As previous post was about fetching covers media from Amazon Web Services, this post will be about fetching covers from popular music site – Last.fm. API documentation page
#!/usr/bin/ruby require 'rubygems' require 'net/http' require 'cgi' require 'xmlsimple' # key from API documentation $lastfm_key = "b25b959554ed76058ac220b7b2e0a026" $lastfm_host = "ws.audioscrobbler.com" def fetch_cover(artist, album) artist = CGI.escape(artist) album = CGI.escape(album) path = "/2.0/?method=album.getinfo&api_key=#{$lastfm_key}&artist=#{artist}&album=#{album}" data = Net::HTTP.get($lastfm_host, path) xml = XmlSimple.xml_in(data) if xml['status'] == 'ok' then album = xml['album'][0] cover = { :small => album['image'][1]['content'], :medium => album['image'][2]['content'], :big => album['image'][3]['content'] } return cover end return nil end puts fetch_cover('Nickelback', 'Dark Horse').inspect
Download ruby script
On my small project i was looking for web service to get media covers from. I found that i can use Amazon Web Services API. The documentation for this ECommerce Service is pretty old, but it still works.
More detailed information about API you can find here
#!/usr/bin/ruby require 'rubygems' require 'net/http' require 'cgi' require 'xmlsimple' $amazon_key = "12DR2PGAQT303YTEWP02" # NOT MY KEY (FOUND ON INTERNET) $amazon_host = "webservices.amazon.com" def fetch_cover(artist, album) artist = CGI.escape(artist) album = CGI.escape(album) path = "/onca/xml?Service=AWSECommerceService&AWSAccessKeyId=#{$amazon_key}&Operation=ItemSearch&SearchIndex=Music&Artist=#{artist}&ResponseGroup=Images&Keywords=#{album}" data = Net::HTTP.get($amazon_host, path) xml = XmlSimple.xml_in(data) if xml['Items'][0]['TotalResults'].to_s.to_i then cover = { :small => xml['Items'][0]['Item'][0]['SmallImage'][0]['URL'], :medium => xml['Items'][0]['Item'][0]['MediumImage'][0]['URL'], :big => xml['Items'][0]['Item'][0]['LargeImage'][0]['URL'] } return cover end return nil end
So, after execution of this function you will get array with 3 different images (small, medium, big).
I use XML-Simple gem for ruby. Can be installed this way
sudo gem install xml-simple
That`s it. Download script
Since i started writing simple manuals about how to make system daemons i found bunch of interesting documents. For today, i just want to publish one of them instead of writing source code. This is manual originally written by Devin Watson, can be very useful for those how have no idea how to develop such system daemons. It`s only a basic information.
http://www.netzmafia.de/skripten/unix/linux-daemon-howto.html
Sometimes it`s necessary to delete all .svn directories that were created by subversion version control system. This shell command will work on all unix systems:
rm -rf `find . -name .svn`
That`s it!
This is a simple piece of code which describing how to update special order field in table. For example, you have table ‘photos’:
+ --------------------------------- + | ID | UserID | OrderID | ImgURL | + --------------------------------- + | 1132 | 1 | 0 | ... | | 2124 | 1 | 0 | ... | | 3456 | 1 | 0 | ... | ..................................... | N | 1 | 0 | ... | + --------------------------------- +
OrderID field value by default is 0. If some images has been deleted order lose its consistency.
To repair order we can use single transaction:
BEGIN; SET @ORDER := 0; UPDATE photos SET order_id = (SELECT @ORDER := @ORDER + 1) WHERE user_id = 1; COMMIT;
After executing this on table ‘images’ we`ll get such result:
+ --------------------------------- + | ID | UserID | OrderID | ImgURL | + --------------------------------- + | 1132 | 1 | 1 | ... | | 2124 | 1 | 2 | ... | | 3456 | 1 | 3 | ... | ..................................... | N | 1 | M | ... | + --------------------------------- +
Some developers instead of using resources of mysql script language trying to solve this problem by executing numerous call, such ‘UPDATE table SET order_id = [value] WHERE id = [id] LIMIT 1;’. It`s wrong. MySQL language have a lot of ways to make it easy. At least UDF`s.
Since i completely switched to ubuntu 8.04 on my laptop i got very weird “click” sounds from hard drive. I thought it was just a simple “sleep” mode, parking heads or something pretty simple. But that sound began to appear so often (sometimes 2 clicks in 1 secons) that i cant even get sleep with that disturbing sound.. But that sound appeared only in ubuntu and never heard it in other os. Wtf is going on? After googling for a short time i figured out what was the problem – Advanced Power Management in Ubuntu.
Solution was very simple. Just turn off this power management:
sudo hdparm -B255 /dev/sda
If you have more than one drive – the same operation but with different device. That`s it.
Ruby is very powerful language, not only for web development as many can think for the first time. It is also providing all necessary resources to build system utilities and daemons. So, this post exactly about it.
Long time ago i was looking for some tool to write simple daemon in a short term. I didn`t choose C just because i was able to develop program only on special computer (i mean “production-like” environment) and the problem wasnt critical to resources. In other words – this daemon was working only few days to complete the task. Ok, lets see what we`ve got:
#!/usr/bin/ruby # --------------------------------------------------------------------- # MODULES # --------------------------------------------------------------------- require 'daemonize' include Daemonize include Process # --------------------------------------------------------------------- # CONFIGURATION # --------------------------------------------------------------------- $daemon = { :name => "Test Daemon", # daemon name :abbr => "testd", # daemon abbreviation :author => "(c) 2008 author", # daemon author :version => "0.1", # actual version :file_log => "/var/log/testdaemon.log", # log path :file_pid => "/var/run/testdaemon.pid", # process id path :delay_sleep => 1, # seconds :user => 'tux', # working data user :grp => 'tux', # working data group :background => false, # background mode :work => true # daemon work flag } $daemon_log = nil $daemon_pid = nil # --------------------------------------------------------------------- def daemon_log(str) puts "[#{Time.now.strftime("%m/%d/%Y-%H:%M:%S")}] #{str}" end def daemon_terminate $daemon[:work] = false end def daemon_stop daemon_log("Stopping working process...") $daemon_pid.close File.delete($daemon[:file_pid]) end def daemon_start if File.exist?($daemon[:file_pid]) then daemon_log("Process already running. If it`s not - remove the pid file") exit end daemon_log("Starting process...") daemonize if $daemon[:background] begin $daemon_pid = File.new($daemon[:file_pid],"w") rescue Errno::EACCES daemon_log("Cannot create PID file. Check the permissions and try again!") $daemon_pid = nil exit end daemon_work end def daemon_work if ($daemon_pid) then $daemon_pid.sync = true $daemon_pid.puts(Process.pid.to_s) begin while $daemon[:work] do daemon_log("Daemon working") daemon_handle_signals sleep($daemon[:delay_sleep]) end rescue Exception => e daemon_log("Error: #{e.message}") end daemon_stop end end def daemon_handle_signals # termination signal Signal.trap("TERM") do daemon_log("TERM signal received.") daemon_terminate end # kill signal Signal.trap("KILL") do daemon_log("KILL signal received.") daemon_terminate end # keyboard interruption Signal.trap("INT") do daemon_log("SIGINT signal received.") daemon_terminate end Signal.trap("TSTP") do daemon_log("SIGTSTP signal received.") end end def daemon_show_version puts "#{$daemon[:name]} v#{$daemon[:version]} #{$daemon[:author]}" end def daemon_show_usage daemon_show_version puts "Usage:" puts " -b, --background work in background mode" puts " -v, --version view version of daemon" puts " -h, --help view this help" end def daemon_parse_opts return true if ARGV.length == 0 case ARGV[0] when '-b', '--background' $daemon[:background] = true; return true when '-v', '--version' daemon_show_version when '-h', '--help' daemon_show_usage else puts "Invalid argument: #{ARGV[0]}" if !ARGV[0].nil? daemon_show_usage end return false end def daemon_main daemon_start if daemon_parse_opts end daemon_main
This is just a basic structure of daemon, it supports background mode. I removed all unimportant information and left only main program cycles. As you can see, the entry point of whole program – daemon_main procedure. It parsing the command line parameters. In this example there is no required parameters, so daemon will run in basic mode (not background). To enable background you should specify the -d (or –background) option. Also, very important – this example needs to be executed under root or other user that have access to /var/run. Other way, PID file path can be changed to whatever you want (file_pid key). All daemon configuration variables stored in array $daemon. Also, it supports system signals handling, like SIGTERM or SIGKILL (all ruby signal constants u can explore here).
I think that`s it. Not a lot, but very simple. Download script: http://files.sosedoff.com/b57415aa/
