Java Runtime.getRuntime().exec() fails after calling it several hundred times

Question

I have a Java program that executes Runtime.getRuntime().exec("ls -l"); many times, once for each directory in the system.

My test system has more than 1,000 directories and Runtime.getRuntime().exec("ls -l"); seems to error out after 480 directories or so. The error message I'm getting is is "Error running exec(). Command: [ls, -l] Working Directory: null Environment: null". I'm guessing it's running out of some required system resources or is it? Is there any way to process all directories without erroring out?

Relative comment from an answer:

I should clarify that I was using Android SDK's adb.exe. I wanted to execute something like Runtime.getRuntime().exec("adb shell ls -l") multiple times on different directories.

Answer 1

You should explicitly close the input/output streams when using Runtime.getRuntime().exec.

Process p = null;
try {
    p = Runtime.getRuntime().exec("ls -l");
    //process output here
    p.waitFor();
} finally {
    if (p != null) {
        p.getOutputStream().close();
        p.getInputStream().close();
        p.getErrorStream().close(); 
    }
}

Answer 2

It would be better to use java.io.File and the appropriate methods on those classes for walking and manipulating the file system.

You don't say why you are doing this degenerate behavior this way but here is an example of listing all the files in a tree.

Answer 3

I have a Java program that executes Runtime.getRuntime().exec("ls -l"); many times, once for each directory in the system.

Why? Something wrong with File.listFiles()?

You don't need to execute 'ls' even once.