How to include a jar when running a Java file per command line

Question

Every time I run the program I need to call a specific library, which in this case is /home/usuario/Programas/weka-x-x-x/weka.jar, but every time I run the program, I have to include the following command java -cp /home/usuario/Programas/weka-x-x-x/weka.jar for libraries to be executed.

I would like to know how to make this library included by default in CLASSPATH, I found this command in Stack Overflow:

export CLASSPATH="dir1;dir2;path/to/jar/containing/AnotherClass;... but it didn’t work.

Answer 1

Define libraries without changing Java

It is not recommended to define a classpath global. May cause unwanted side effects in other programs.

To avoid repetition, create a file shell script containing the commands you need, use the chmod to set running permissions for the file and use the new "executable" instead of calling Java directly when you need it.

Using the variable CLASSPATH

If you still want to define a classpath global, the correct is using the environment variable CLASSPATH. However, change the semicolon by colon in the directory separation, as follows:

export CLASSPATH="dir1:dir2:path/to/jar/containing/AnotherClass:...

Semicolon is used in Windows environments while colon is used in Unix/Linux environments.

Also, if you want the environment variable to be present at all linux sessions, even after system reboot, you will need to add the command export in some startup script.

Changing the Java installation

As noted in this reply by Soen, you can put the jar in the folder ext of the Java installation:

JAVA_HOME/jre/lib/ext

Again, I do not advise doing this. Even very common libraries can sometimes generate conflicts. For example, some older project may depend on an older version of the same jar used by a newer application.