Java Streams - Shell Commands

This takes away from the portability of Java applications.
For instance, if you write a Java application on a Unix system, you might be interested in running the "ps -ef" command, and reading the output of the command. For Unix systems this is great however, since this same program will not work on a Windows system because the ps command is not available on Windows. Putting portability aside for this article, we will demonstrate a method that can be used to run system commands.
You can invoke a Unix shell like you would invoke any other program. Use the -c option to pass the command to run as a parameter.
Also make sure to use the exec(String[]) method, and not exec(String), to avoid the command being tokenized the wrong way:

String[] cmd = {"/bin/sh", "-c", "/bin/cat alias > bias"};
Process p = Runtime.getRuntime().exec(cmd);

To read and write from/to the process, get the input, output, and error streams from the Process instance you just created:

InputStream in = p.getInputStream();
InputStream err = p.getErrorStream();
OutputStream out = p.getOutputStream();