The Author – Bart Busschots
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Nov
23
TTT Part 24 of n – Ethernet & ARP
Filed Under System Administration, Computers & Tech on November 23, 2014 | 4 Comments
In the previous instalment we took a big-picture look at how TCP/IP networking works. As a quick reminder, the most important points were:
- Networking is complicated!
- Our computer networks use a stack of protocols known as TCP/IP
- We think of the stack of protocols as being broken into four layers:
- The Link Layer – lets computers that are on the same network send single packets of data to each other
- The Internet Layer – Lets computers on different networks send single packets of data to each other
- The Transport Layer – lets computers send meaningful streams of data between each other
- The Application Layer – where all the networked apps we use live
In this instalment we’ll take a quick look at the lowest of these four layers – the Link Layer. Specifically, we’ll look at MAC addresses, the difference between hubs, switches, and routers, and the ARP protocol.
Oct
25
TTT Part 23 of n – Networking Intro
Filed Under System Administration, Computers & Tech on October 25, 2014 | 11 Comments
This instalment is the first in what will probably be quite a long mini-series on computer networking. Before we can look at the terminal commands that allow us to interact with the network, we need to gain an understanding of how computer networking works. This is a complex topic, ad there’s a lot to take in. The individual pieces don’t make sense without keeping the big-picture in mind, and yet the big picture doesn’t gel together until you start to understand the detail. Bearing that in mind, this instalment starts the series with a big-picture overview. We’ll flesh this overview out over the instalments that follow, adding in the detail that will hopefully make the whole thing click for you. Ultimately, it’s actually a very elegant design, but that elegance may not be immediately obvious!
Oct
10
TTT Part 22 of n – Tips & Tricks
Filed Under Computers & Tech, System Administration on October 10, 2014 | 2 Comments
This instalment is a little breather between the fairly heavy instalments on searching, and the upcoming set of instalments on networking. We’ll start with a look at some tips and tricks for getting the most out of BASH, and then transition to some tips and tricks for getting the most out of the OS X Terminal app.
Sep
26
TTT Part 21 of n – More Searching
Filed Under System Administration, Computers & Tech on September 26, 2014 | 1 Comment
This is the third and final instalment on searching. In the first instalment we learned how to search for text within files and streams using egrep. In the second we learned to search for files based on all sorts of criteria with the find command. In this final instalment we’ll start by looking at one last feature of find, its a ability to execute commands on the files it finds. Then we’ll end by looking at an OS X-only alternative to find that makes use of the Spotlight search index to really speed up searches.
Sep
7
TTT Part 20 of n – File Searches
Filed Under System Administration, Computers & Tech on September 7, 2014 | 2 Comments
In the previous previous instalment we looked at using egrep to search for a particular piece of text in a stream or file. egrep is often a great tool for finding a file you are looking for, but only if the file is a plain text file, and only if you are searching for that file based on its content. What if you want to search for files based on other criteria, like the last time the file was edited, or the name of the file, or the size of the file, or the type of the file etc.? For that you need a different command, for that you need find.
Aug
16
XKPasswd 2 – An Absolute Beginner’s Guide
Filed Under Software Development, Computers & Tech on August 16, 2014 | 2 Comments
I’ve just released version two of the XKPasswd perl module, the module that powers the www.xkpasswd.net website. At the moment, only the module has been updated, not the website. It’s going to take me a few months to make all the changes I want to on that site. In the mean time you, can use the module directly. The prerequisites are that you have a computer with Perl and GIT installed, and a plain text editor (no difficult on Linux or Mac).
Jul
19
TTT Part 19 of n – Text Searches
Filed Under System Administration, Computers & Tech on July 19, 2014 | 1 Comment
In the previous two instalments (17 & 18) of this series we learned how to represent patters with regular expressions, or, to be more specific, with POSIX Extended Regular Expression (or EREs). We used the egrep command to test our regular expressions, but we didn’t discus the command itself in detail. Now that we understand regular expressions, it’s time to take a closer look at both egrep, and it’s older brother grep, both commands for filtering and searching text.
May
10
TTT Part 18 of n – More REs
Filed Under Computers & Tech, System Administration on May 10, 2014 | 4 Comments
In the previous instalment we introduced the concept of Regular Expressions, and started to learn the POSIX ERE regular expression language, noting that POSIX ERE is a sub-set of the very commonly used Per Compatible Regular Expression (PCRE) language.
In this instalment we’ll learn more POSIX ERE syntax, and have a look at some examples of REs in GUI apps.
Apr
27
TTT Part 17 of n – Regular Expressions
Filed Under System Administration, Computers & Tech on April 27, 2014 | 5 Comments
This instalment is the start of a series of instalments relating to searching from the command line. Searching is all about patterns, and that means getting to grips with Regular Expressions (also called RegExps, RegExes or REs for short). Regular Expressions are languages for representing patterns, and are used throughout IT, not just on the command line. While this series focuses on the Terminal, an understanding of regular expressions will be helpful in many other places, from programming languages to GUI apps like programming editors, search utilities or file re-namers. It’s going to take us two instalments to properly describe regular expressions, but when we’re done we’ll have gained a very useful skill.
Feb
8
TTT Part 16 of n – Crossing the Streams
Filed Under System Administration, Computers & Tech on February 8, 2014 | 2 Comments
In the previous instalment we introduced the concepts of streams, and looked at how every process has references to three streams as part of their environment – STDIN, STDOUT & STDERR. We went on to introduce the concept of operators that manipulate these streams, and we focused on the so-called ‘pipe’ operator which connects STDOUT in one process to STDIN in another, allowing commands to be chained together to perform more complex tasks. We mentioned the existence of operators for connecting streams to files, and the possibility of streams being merged together, but didn’t go into any detail. Well, that’s what we’ll be doing in this instalment.