You've probably come across strange posts on various social media platforms recently where users have shared images of what at first glance appears to be a very simple word game. Typically, you'll see a grid of five by six boxes colored either gray, yellow, or green populated by five-letter words that don't seem to have anything in common.

If you've steered clear of the hype so far, this phenomenon goes by the name of Wordle [1]. Launched in October 2021, the free and currently ad-free Wordle was quickly acquired by The New York Times Company from US software developer Josh Wardle for a "low seven-figure sum" – rumors on the web claim the actual sum was $6 million [2].

To solve Wordle puzzles, you need an extensive vocabulary. If you want to make things a little easier, you can use a dictionary file and some regular expressions and create your own Wordle solver. From an IT point of view, Wordle offers an ideal practical example for getting started with grep and regular expressions.

Numerous Wordle Clones

All the hubbub about Wordle and the game's simple structure have already prompted numerous developers to program clones. In addition to various web-based imitations, there are also apps for mobile operating systems such as Android and iOS. There are even native Wordle imitators for Linux, such as Warble [3]. Like the original, all of these applications use an English-language dictionary (Figure 1).

Figure 1: Warble imitates Wordle on Linux (left). Sites like The Word Finder help to solve the ubiquitous language puzzle (right).

The easiest approach to implementing a Wordle game is probably via the command line because the game does not need complex graphics. For Linux, an open source Wordle [4] (Figure 2) can be downloaded with a few simple commands (Listing 1).

01 $ wget https://github.com/ivanjermakov/wordle/releases/latest/download/wordle
02 $ chmod +x wordle
03 $ ./wordle

Figure 2: Wordle does not require complex graphics or animations, which explains why there are now Wordle games for the Linux terminal.

In addition to clones, sites such as The Word Finder [5] or Wordle Solver [6] can help you find a solution (the source code for Wordle Solver is available on GitHub [7]).

Basics of the Game

To solve a Wordle, you don't have to learn complicated rules. You have six attempts at each Wordle. In the first step, just enter an arbitrary five-letter word in the top line. On your first attempt, there are no clues; your first guess is completely random.

After pressing Enter, Wordle checks the input. If a field lights up green, the letter you entered is correct and is in the right place. If the field shows up yellow, the letter is part of the word, but currently in the wrong place. A letter with a dark gray background, on the other hand, is not part of the target word. With the help of these hints, you can narrow down the target word in the following lines until all of the letter fields light up green and you have solved the Wordle. You have a total of six attempts (Figure 3); there is always only one Wordle a day (see the "Second Chance" box).

Figure 3: A first attempt: All the fields are still empty in the beginning. Enter a random word as the first guess.

Using Regexes

You can solve a Wordle using the Linux grep tool and a couple of simple regular expressions (regexes), which can be used to automatically process and filter texts and strings. If you have not worked with these tools previously, they are indispensable in the everyday life of software developers. Using these tools to solve a Wordle is a wonderful introduction to this topic with huge practical benefits. To solve a Wordle, we will work our way through the hints step by step, and at the end the computer will output the solution.

For this to work, however, you first need a dictionary. A dictionary may not exist on your Linux system, but check out /usr/share/dict/ first – you might find a file that fits the bill. For a word list, you will use words_alpha.txt, which you can get from GitHub [8]. This lists contains over 370,000 words, including some pretty quirky ones, as you'll see later.