Dev Notes

Various Cheat Sheets and Resources by David Egan/Carawebs.

This website contains notes & cheatsheets for web development, Linux systems administration, information security and cryptocurrency.

This site is maintained by David Egan:


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Information Entropy

12 Aug 2019

Information Entropy is the average rate at which information is produced by a stochastic(random) source of data.

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Lambdas in C++

09 Aug 2019

In C++ a lambda expression or lambda function is a closure: an unnamed (anonymous) function that is passed inline - usually to another function. Lambda expressions are a concise way of creating simple function objects.

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Build an Array of Strings From a File in C

29 Jul 2019

Use getline() to read lines from a file, and add them to dynamically allocated memory:

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Radix 64 Encoding: Implementation in C

21 Aug 2018

Radix 64 or base 64 is a binary-to-text encoding system that is designed to allow binary data to be represented in ASCII string format. This is an educational project accepts a string from a user and Radix 64 encodes it.

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First & Last Element in C++ Iterator Loop

19 Jul 2018

When looping with an iterator, the index of the current iteration isn't immediately obvious unless you resort to incrementing a counter. Fortunately it's easy to find the start and end of your loop.

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HTTP Server in C

12 Jun 2018

Simple http server socket in Linux. This is an educational work in progress, and these are my notes.

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List & Dict Comprehensions in Python

27 May 2018

Python comprehensions are syntactic sugar constructs that provide a way to build a list, dictionary or set from a starting list, dictionary or set whilst altering or filtering elements.

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Javascript Resources

01 Apr 2018

Collection of resources for learning Javascript.

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Define User Input From an Integer List in C++

04 Feb 2018

There are many ways to collect user input. In this example a user is prompted to make a selection from a numbered list. This sets the int choice variable, which can then be used to control programme flow.

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Encrypted Backup Drive in Ubuntu Xenial 16.04

15 Oct 2017

Protect your sensitive data - create a LUKS encrypted backup partition for Ubuntu 16.04 Xenial Xerus that is automatically mounted on boot.

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Bitcoin Cold Wallet Setup Bash Script

22 Aug 2017

Access a Bitcoin core wallet in an airgapped environment. Secure management of cold-wallets.

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Ignore IP Addresses in Fail2Ban

20 Jul 2017

Fail2Ban can help protect your Linux server from attack. It's a Python package that monitors log files and dynamically adjusts firewall rules to block malicious IP addresses. This article shows how to configure Fail2Ban so that specified IP addresses are ignored.

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Install and Run Geth (golang implemenation of Ethereum) on Ubuntu

03 Jul 2017

Ethereum is a decentralized blockchain-based platform that runs smart contracts. Because of the decentralized nature of Ethereum, smart contracts run exactly as programmed - short of an internet apocalypse, there is no possibility of downtime, censorship, fraud or third-party interference. The network is cryptographically secure, decentralized and tamper-proof.

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Verification of Bitcoin Core Download in Ubuntu

01 Jul 2017

Install Bitcoin Core in Ubuntu 16.04 - how to download and verify from bitcoin.org.

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Enable all Apache Config Files

22 Jun 2017

Enable all Apache virtual host configurations at once. This article provides a useful BASH script that loops through and enables all vhost configs - useful when setting up new development machines or changing servers.

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