Why is the Java runtime not passing parameters with spaces to the script?

The Java runtime, when executing external scripts or commands using methods like Runtime.getRuntime().exec() or ProcessBuilder, often encounters issues with parameters containing spaces. This is because these methods typically tokenize the command string based on spaces, treating each space-separated part as a separate argument. When a parameter itself contains spaces, it gets incorrectly split into multiple arguments, leading to unexpected behavior in the script.

Here's a breakdown of why this happens and how to address it:

1. String Tokenization:

- When you pass a command string to Runtime.getRuntime().exec(), the Java runtime parses this string based on spaces. For example, if you pass "myScript.sh arg1 arg with spaces arg3", it might interpret this as four separate arguments: myScript.sh, arg1, arg, and with, spaces, and arg3. This is not what you intend if arg with spaces is meant to be a single parameter.

2. ProcessBuilder's Argument Handling:

- ProcessBuilder is generally preferred over Runtime.getRuntime().exec() because it provides more control over the process creation. However, if you pass a single string to the ProcessBuilder constructor, it will also tokenize the string based on spaces, similar to exec().

3. Correct Approach: Using String Arrays or Lists:

- To correctly pass parameters with spaces, you should use a string array or a list of strings with ProcessBuilder. Each element in the array or list represents a single argument. This prevents the Java runtime from splitting the parameters incorrectly.

4. Example using ProcessBuilder:

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

public class ScriptExecutor {
  public static void main(String[] args) throws IOException {
    String scriptPath = "/path/to/myScript.sh";
    String arg1 = "value1";
    String argWithSpaces = "value with spaces";
    String arg3 = "value3";

    // Correct way to pass arguments with spaces
    List<String> commandList = Arrays.asList(scriptPath, arg1, argWithSpaces, arg3);
    ProcessBuilder builder = new ProcessBuilder(commandList);
    Process process = builder.start();

    // Handle process output and errors here
  }
}

5. Explanation of the Code:

- The code creates a List<String> called commandList, where each element is a separate argument, including the script path and the parameters. The parameter argWithSpaces, which contains spaces, is treated as a single argument.

- The ProcessBuilder is initialized with this list, ensuring that the arguments are passed correctly to the script.

By using a string array or list with ProcessBuilder, you can avoid the issue of the Java runtime incorrectly splitting parameters with spaces, ensuring that your scripts receive the arguments as intended.

Learn more about this