Shell script to compile Java

Question

cd "$(dirname "$0")"
javac -d . -sourcepath Source Source/project/Main.java
rm "Project.jar" 2>"/dev/null"
jar cfm "Project.jar" "Manifest.txt" project/*

This script would be placed in a Project directory, in which is Manifest.txt and a Source directory which contains the base package, i.e., Main.java would start with package project;. The script would compile the Java into classes, creating a directory of name project inside the Project directory, and then from the class files create Project.jar. I do not have any IDEs installed, but is this typically how they work to compile a project with multiple .java files into a single .jar file?

Answer 1

No #! line to specify interpreter. Perhaps not so important for something that's portable shell, but still helpful to write #!/bin/sh.

No checking that cd was successful. We really don't want to continue if that fails for any reason. Similarly if javac fails, we want to exit with non-zero status. We could add || exit after all commands, but it's easier and simpler to begin the script with set -e.

I'm guessing the redirection of rm's standard error is to cope with Project.jar not existing. I suggest using rm -f instead, which is silent in that case (but will remove read-only files, assuming the directory is writable).

Using shell might work for the short term, but as your project grows, you'll find that going through all the steps unconditionally becomes more and more time-consuming. That's the point to move to a tool that's designed for resolving dependencies and orchestrating builds, such as Ant or Make; other tools are available and recommended by Torben which might also be suitable.

Answer 2

Using custom shell scripts is not a typical way to compile and package multiple source files into a Jar-package. The de-facto standard tools for building Java projects and managing their dependencies are Maven and Gradle. Maven being mostly Java-centric and Gradle being truly "multi-language." The learning curve may seem steep compared to just writing a shell script but the payoff comes as soon as you need to add a 3rd party Jar file (junit and logging are almost always the first ones) to your project.

Regarding the shell script in itself, Toby's answer is spot on.