Know process id by port number

Some time we want to know the process id using port number.Following is the command to use

Syntax:  $ lsof -i tcp:PORT_NUMBER

Example: lsof -i tcp:3000

Output:
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
firefox-b        1837  ravi     46u   IPv4  87572      0t0    TCP localhost:51945->localhost:3000 (ESTABLISHED)
ruby             2846  ravi     8u     IPv4  49836      0t0    TCP *:3000 (LISTEN)
ruby             2846  ravi     9u     IPv4  78566      0t0    TCP localhost:3000->localhost:58605 (CLOSE_WAIT)

In output we can see 2846 is the ruby server id.

readline error for ruby

Following is the error:
`require': cannot load such file -- readline (LoadError)

Solution:

sudo apt-get install libreadline-dev libncurses-dev libreadline5 libreadline5-dpg

cd <ruby source directory>/ext/readline
ruby extconf.rb
make
sudo make install

rvm pkg install readline

Solved Open ssl load error with rvm

Step 1 : Install openssl package

rvm pkg install openssl

Step 2: remove ruby

rvm remove 1.9.3

Step 3:

rvm install 1.9.3 --with-openssl-dir=$HOME/.rvm/usr

How to use will paginate with array of hashes

Suppose we have an object  which is having value as array of hashes (In example @student['results'] is an array of hashes which is returned from some API call)

so the is given below

  @students = WillPaginate::Collection.create(@page, @page_size) do |pager|
        # inject the result array into the paginated collection:
        pager.replace(@student['results'])
        unless pager.total_entries
          # the pager didn't manage to guess the total count, do it manually
          pager.total_entries = (@student['total_pages'] * @page_size)
        end
      end