How does the Java VM decides the value of the user.dir System property?

Question

I'm running a simple Java program with below directory structure:

MyProject (A project in my Eclipse IDE)
 '-- src
      '-- Hello.java

In Hello.java I'm printing the value of 'user.dir' System property.

System.out.println(System.getProperty("user.dir"));

Compiled file for my class is getting stored in MyProject\bin folder.

When I'm running this class from Eclipse (Right click on source file and click on Run As->Java Application), it prints the path up to 'MyProject' folder, i.e. D:\Projects\Workspace\MyProject in console window.

Then I used the command window to run the same program. This is what I typed on window:

D:\Projects\Workspace\MyProject\bin>java Hello

and output on console is: D:\Projects\Workspace\MyProject\bin

bin has been added to previous value for user.dir.

Further, to check more, I this time executed the Java command from a different folder on command window:

D:\Projects\Workspace\MyProject>java -classpath D:\Projects\Workspace\MyProject\bin Hello

This time output on command window is: D:\Projects\Workspace\MyProject

This value changes when I changed the folder on command window, and when I'm running the program from Eclipse, the value for user.dir is the project folder. So I would like to understand, what is the basis for deriving the value of 'user.dir'? How does JVM decides, what should be the value for user.dir?

Answer 1

As defined by java.lang.System specification the user.dir property returns the current working directory (i.e. the current directory when JVM was started):

user.dir User's current working directory

I see nothing contradictory in your example. The only thing unclear here is the name of the property. I don't understand why they chose to put 'user' in there.

Similarly if you executed the same Java program from totally different path you would get the other path as the outcome. Try this yourself:

 c:
 cd c:\
 java -cp D:\Projects\Workspace\MyProject\bin Hello

What Eclipse does before running your program is something similar to:

 d:
 cd d:\projects\workspace\myproject
 java -cp d:\projects\workspace\myproject\bin Hello

Answer 2

The property user.dir is defined to be the current working directory. The javadoc for System details the various different system properties.

Maybe you actually want user.home?