How to begin developing a computer version of the popular card game. Between the previous 163 columns I've written here in Linux Journal and the dozens of games I programmed and explored during the creation of my Wicked Cool Shell Scripts book, I've written a lot of Bash shell games. The challenge is to find one that's simple enough where a shell script will work, but isn't so simple that it ends up being only a half-dozen lines.

Finally, I'm going to finish the mail merge script, just in time for Replicant Day.

Dave tackles analysis of the ugly Apache web server log. I know, in my last article I promised I'd jump back into the mail merge program I started building a while back. Since I'm having some hiccups with my AskDaveTaylor.com web server, however, I'm going to claim editorial privilege and bump that yet again.

  You've seen it a million times—the hash-bang (#!) line at the top of a script—whether it be Bash, Python, Perl or some other scripting language. And, I'm sure you know what its purpose is: it specifies the script interpreter that's used to execute the script. But, do you know how it actually works? Your initial thought might be that your shell (bash) reads that line and then executes the specified interpreter, but that's not at all how it works. How it actually works is the main focus of this post, but I also want to introduce how you can create your own version of "hash-bang" if you're so inclined.

Creating a sed-based file substitution tool. A few weeks ago, I was digging through my spam folder and found an email message that started out like this:

Decimals to Roman numerals—here we hit all the limitations of Bash shell scripting.

Don't expose your system with sloppy scripts!

When in Rome: finishing the Roman numeral converter script. In my last article, I started digging in to a classic computer science puzzle: converting Roman numerals to Arabic numerals. First off, it more accurately should be called Hindu-Arabic, and it's worth mentioning that it's believed to have been invented somewhere between the first and fourth century—a counting system based on 0..9 values.

Fun with retro-coding a Roman numeral converter—I head back to my college years and solve me homework anew! I earned a bachelor's degree in computer science back in the dawn of computing. Well, maybe it wasn't quite that long ago, but we did talk about Ada and FORTRAN in class. As a UCSD alumnus, however, it's no surprise that UCSD Pascal was the programming language of choice. Don't worry; no punch cards and no paper tape were involved in my educational endeavors.

URLify: convert letter sequences into safe URLs with hex equivalents. This is my 155th column. That means I've been writing for Linux Journal for: $ echo "155/12" | bc 12 No, wait, that's not right. Let's try that again:

I recently created a video demonstration of how to do some work at the command line, but as I tried to record my video, I kept running into problems. I'm just not the kind of person who can type commands at a keyboard and talk about it at the same time. I quickly realized I needed a way to simulate typing, so I could create a "canned" demonstration that I could narrate in my video.

Exploring the nuances of writing a pair-matching memory game and one-dimensional arrays in Bash. I've always been a fan of Rudyard Kipling. He wrote some great novels and stories, mostly about British colonial-era India. Politically correct in our modern times? Not so much, but still, his books are good fun for readers and still are considered great literature of its time. His works include The Jungle Book, Captains Courageous, The Just So Stories and The Man Who Would Be King, among many others.

You can shuffle your feet and you can shuffle cards, but can you shuffle characters? Dave's latest column explores the possibilities. My last few articles have described building a pretty sophisticated password generator, except for one thing: I never quite got to the point of scrambling the end result to add a second level of randomness. I sidestepped the issue by saying it was an exercise for the reader, but in fact, it's a pretty interesting problem, so let's look at it here. You can reverse a word with the handy Linux command rev, like so:

Mnemonic passwords generally stink. A random sequence of letters, digits and punctuation is more secure—just don't write down your passwords, like the knucklehead antagonist does in Ready Player One!

Passwords. They're the bane of computer users and a necessary evil, but they have risks and challenges associated with them. None of the choices are great. If it's up to your memory, you'll end up using the same password again and again. Use a password manager like 1Password, and you're reliant on its database security and portability. Two-factor? Um, can I borrow your phone for a minute?

Dave starts a new method for generating secure passwords with the help of 1Password. A while back I shared a script concept that would let you enter a proposed password for an account and evaluate whether it was very good (well, maybe "secure" would be a better word to describe the set of tests to ensure that the proposed password included uppercase, lowercase, a digit and a punctuation symbol to make it more unguessable).

Dave wraps up the shell-script L33t generator Last time, I talked about what's known informally as l33t-speak, a series of letter and letter-pair substitutions that marks the jargon of the hacker elite (or some subset of hacker elite, because I'm pretty sure that real computer security experts don't need to substitute vowels with digits to sound cool and hip).

Dave continues with his shell-script L33t translator. In my last article, I talked about the inside jargon of hackers and computer geeks known as "Leet Speak" or just "Leet". Of course, that's a shortened version of the word Elite, and it's best written as L33T or perhaps L337 to be ultimately kewl. But hey, I don't judge.

How to script a l33t-speak translator. My daughter and I were bantering with each other via text message this morning as we often do, and I dropped into a sort of mock "leet speak". She wasn't impressed, but it got me thinking about formulaic substitutions in language and how they represent interesting programming challenges.

Boasting as many pages as most technical books, this month’s issue of Linux Journal comes in at a hefty 181—that’s 23 articles exploring topics near and dear to everyone from home automation hobbyists to Free Software advocates to hard-core hackers to high-level systems architects.