Instructions to Install JLex on Linux

Want all the instructions in one code block without the explanations? Check out the appendix.

Before Starting

Prerequesite Software

These instructions are for Linux machines. If you’re a Windows user, I recommend using the Windows Subsystem for Linux (WSL). The only prerequesite software required is Java. If you’re on a Debian-based system and don’t have Java installed, you can install it via sudo apt install default-jre and sudo apt install default-jdk.

Organization

You may want to create a separate “2140” directory for this class:

mkdir -p 2140
cd 2140

Make sure you download the following two files:

You can download files on the CS servers by running curl url -o filename, where url is replaced with the url of the file you want to download, and filename is the filename of the file you’re downloading.
So, to download these two files, you can run:

curl https://blog.bornais.ca/2140/lex/Main.java -o Main.java
curl https://blog.bornais.ca/2140/lex/simple.lex -o simple.lex

Instructions

Create a “JLex” directory (case sensitive!):

mkdir -p JLex

Move “Main.java” (attached) into the JLex directory

 mv Main.java JLex

cd into the JLex directory

cd JLex

Compile “Main.java”

javac Main.java

Move back to the parent directory

cd ..

JLex is now installed! You can now run the scanner generator.
The general method to do this is to run: java JLex.Main lexFileName, replacing lexFileName with the name of your lex file.
We’ll use the sample lex file simple.lex, courtesy of Dr. Jianguo Lu, which we downloaded earlier.
To run this file, simply type:

java JLex.Main simple.lex

You should now see a new file generated, called lexFileName.java, or in this case simple.lex.java. We must now compile it, by typing:

javac simple.lex.java

A new file, MyLexer.class should have been created (note, if using a lex file other than simple.lex, this file may be named something different). We can now run the lexer by running:

java MyLexer

That’s it!

Now try typing stuff on your keyboard and see how the lexer responds. Try typing “int” or typing some words, like “hello” and “world”.

Appendix

All the commands in one block

mkdir -p 2140
cd 2140

curl https://blog.bornais.ca/2140/lex/Main.java -o Main.java
curl https://blog.bornais.ca/2140/lex/simple.lex -o simple.lex

mkdir -p JLex
mv Main.java JLex
cd JLex
javac Main.java
cd ..

java JLex.Main simple.lex
javac simple.lex.java
java MyLexer

Before Starting#

Prerequesite Software#

Organization#

Instructions#

That’s it!#

Appendix#

All the commands in one block#