How to use "cd" command using Java runtime?

Question

I've created a standalone java application in which I'm trying to change the directory using the "cd" command in Ubuntu 10.04 terminal. I've used the following code.

String[] command = new String[]{"cd",path}; Process child = Runtime.getRuntime().exec(command, null); 

But the above code gives the following error

Exception in thread "main" java.io.IOException: Cannot run program "cd": java.io.IOException: error=2, No such file or directory 

Can anyone please tell me how to implement it?

Answer 1

There is no executable called cd, because it can't be implemented in a separate process.

The problem is that each process has its own current working directory and implementing cd as a separate process would only ever change that processes current working directory.

In a Java program you can't change your current working directory and you shouldn't need to. Simply use absolute file paths.

The one case where the current working directory matters is executing an external process (using ProcessBuilder or Runtime.exec()). In those cases you can specify the working directory to use for the newly started process explicitly (ProcessBuilder.directory() and the three-argument Runtime.exec() respectively).

Note: the current working directory can be read from the system property user.dir. You might feel tempted to set that system property. Note that doing so will lead to very bad inconsistencies, because it's not meant to be writable.