How to call System commands from a java program

Question

I want to use system commands like mkdir and remdir running a java program.

How can I do that?

Answer 1

Why do you want to use the command line? FYI, there are built-in platform-independent File classes.

http://www.exampledepot.com/egs/java.io/deletefile.html
http://www.roseindia.net/java/beginners/java-create-directory.shtml

Make directory:

new File("dir path").mkdir();

Remove directory:

new File("dir path").delete(); 

'new File' here is a bit of a misnomer, it isn't actually creating the directory or a file. It's creating a Java resource hook which you can use to query or operate upon an existing filesystem resource, or create a new one at your request. Otherwise, use Runtime.getRuntime().exec("command line here") for using command line operations (not advised!!).

Edit: sorted out the problem the question poster was having:

String envp[] = new String[1];
envp[0] = "PATH=" + System.getProperty("java.library.path");
Runtime.getRuntime().exec("command line here", envp);

Note the insertion of envp into the exec(..) method call, which is basically the PATH variable from the environment.

Answer 2

The best is not to, but rather find the pure Java API function that does it. It is cleaner, easier to understand and much less error prone. It is also the only way to do Java that is write once run everywhere. Once you are calling shell commands, you are tied to that shell.

In your case you are looking for the java.io.File class, and specifically the mkdir and delete methods.

Answer 3

There are methods for this in the Java API, and nicely wrapped implementations in commons-io that simplify the process further.

http://commons.apache.org/io/api-1.4/org/apache/commons/io/FileUtils.html

Answer 4

As the other mentioned, you shouldn't do this for simple file management. But to have it mentioned: The Java API has a class called Runtime, that allows system calls... e.g. Runtime.getRuntime().exec("some_command");