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rails profiling

Installing ruby-prof

First install ruby-prof 0.6.1:

   1  git clone git://github.com/jeremy/ruby-prof.git
   2  cd ruby-prof/
   3  rake gem
   4  sudo gem install pkg/ruby-prof-0.6.1.gem

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ssh -NC user@host -L 8000:127.0.0.1:3306

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# convert to integer: 12, 0x03
# raise an error if the string contains something other that a valid number
n = Integer(string)

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list which application listen on which port:
lsof -nPi | grep LISTEN

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ssh -p 2451 [email protected] 'sudo dd if=/dev/xenvg/box | gzip -c' | gzip -d | dd of=/dev/sda

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detach subdirectory:


You want to clone your repository and then use git filter-branch to mark everything but the subdirectory you want in your new repo to be garbage-collected. To clone your local repository:

 $ git clone --no-hardlinks /XYZ /ABC

The --no-hardlinks switch makes git use real file copies instead of hardlinking when cloning a local repository. The garbage collection and pruning actions will only work on blobs (file contents), not links.

Then just filter-branch and reset to exclude the other files, so they can be pruned:

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Surround a heredoc with quotes and you can continue the code on the same line:

    render :status => 404, :text => <<-'EOH' and return unless setup
        article not found<br/>
        I, as a server, have failed<br/>
        https?
        EOH

Quotes also give you more freedom/creativity with the terminal ID:

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# some more: http://cheat.errtheblog.com/s/datamapper/

# results of first steps with datamapper and lack of documentation

# use a bigint unsigned column as primary key
property :id,               Serial, :min => 0, :max => 2**32

# automagically create database from your model definitions (destructive !)
DataMapper.auto_migrates!
<Model>.auto_migrate!

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# some nice ruby 1.9 additions

str = arr.map(&:firstname)  # if arr is an array of user object (worked in ruby 1.8 with activesupport but now native in ruby 1.9)

# map, each, etc... returns an iterator object with a with_index method
arr.map.with_index {|element, i| ... }
arr.each.with_index {|element, i| ... }

# lambda can have default parameters
p = proc{|a, b = 3| ... }

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# client
require 'zmq'
ctx = ZMQ::Context.new(1)
s = ctx.socket(ZMQ::REQ);
# max queue size
s.setsockopt(ZMQ::HWM, 100);

s.connect("tcp://127.0.0.1:7000");

msg = "msg_content"