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Open Classes (also known as Monkey Patching)

Instead of creating a class that performs common operations on strings like this:

class StringUtils
  def self.to_alphanumeric(s)
    s.gsub(/[^\w\s]/, '')
  end
end

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To avoid the logs growing too large logrotation can be configured with Linux's logrotate tool. The logrotation configuration file is located at: /etc/logrotate.d/your_app_name Example of logrotate configuration file for a Rails app (remember to remove the comments!):

# monitor the /home/deploy/path/to/my/app/shared/log/*.log file
/home/deploy/path/to/my/app/shared/log/*.log {
        weekly # rotate weekly
        missingok #  avoids halting on any error and carries on with the next log file
        rotate 52 # 52 days worth of logs would be kept
 compress # compress using gzip

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Chapter 1: Driving Code Through Tests

retry and redo

redo and retry are both used to re-execute parts of a loop. But they differ in how much they re-execute: redo only repeats the current iteration, while retry repeats the whole loop from the start.

redo example:

(0..5).each do |i|

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Redis Installation (Ubuntu)

• sudo apt-get install -y python-software-properties
• sudo add-apt-repository -y ppa:rwky/redis
• sudo apt-get update
• sudo apt-get install -y redis-server

Start Redis Server

For development

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# CLOSURES IN RUBY     Paul Cantrell    https://innig.net
# Email: username "cantrell", domain name "pobox.com"
 
# I recommend executing this file, then reading it alongside its output.
#
# Alteratively, you can give yourself a sort of Ruby test by deleting all the comments,
# then trying to guess the output of the code!
 
# A closure is a block of code which meets three criteria:
#

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Name	Aliases	Description
$!	$ERROR_INFO	The exception information message set by the last 'raise' (last exception thrown).
$@	$ERROR_POSITION	Array of the backtrace of the last exception thrown.
$&	$MATCH	The string matched by the last successful pattern match in this scope.
$`	$PREMATCH	The string to the left of the last successful match.
$'	$POSTMATCH	The string to the right of the last successful match.
$+	$LAST_PAREN_MATCH	The last group of the last successful match.
$1 to $9		The Nth group of the last successful regexp match.
$~	$LAST_MATCH_INFO	The information about the last match in the current scope.

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In order to have your cache always created with a group of www-data you need to do the following:

cd yourrailsapp
chgrp www-data ./tmp
sudo chmod g+s tmp

This sets the group id on your folder so that everything underneath tmp gets created with the correct permissions

References:

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Using curl to log in setting the cookie and extracting the CSRF token:

curl http://localhost:3000/users/sign_in --cookie-jar cookie | grep csrf

curl http://localhost:3000/users/sign_in -L --data "user[email]=user@users.com&user[password]=my_password&authenticity_token=oy4J2HVPezOc5JrTXMyaSjeCDHhN%2Bv5yVzlvShm%2FjFc%3D" --cookie cookie

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To create a Read only user

Access postgres console:

sudo -u postgres psql

Create user and grant read access to the database

CREATE USER user_name WITH ENCRYPTED PASSWORD 'your_password';
CREATE DATABASE user_name;

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###du Summarize disk usage of each FILE, recursively for directories sorted by size

sudo du -x -h / | sort -n | tail -40

###truncate Truncate files to size 0MB

truncate -s 0 production.log