Runtime.exec() vs ProcessBuilder: Why Does My Command Exit with Code 1001?

ProcessBuilder vs Runtime.exec(): A Comparison

When executing external commands from Java, developers often encounter a dilemma between using Runtime.getRuntime().exec(...) and new ProcessBuilder(...).start(). To shed light on the differences between these two approaches, let's examine their behavior in detail.

Case Study

In a use case where both Runtime.exec() and ProcessBuilder are employed to execute a specific command, a notable difference arises. With Runtime.exec(), the command terminates successfully with an exit value of 0. However, when using ProcessBuilder, the exit value is 1001, and the command terminates prematurely.

Root Cause

The discrepancy lies in the way exec() and ProcessBuilder handle command arguments. exec() accepts a single string or an array of strings, tokenizing the input into arguments. In contrast, ProcessBuilder expects either a varargs array of strings or a List, where each element is considered an individual argument.

Solution

To resolve the issue with ProcessBuilder, ensure that the command arguments are provided as separate strings. For instance, instead of the following:

Process p = new ProcessBuilder(
    "C:\DoStuff.exe -arg1 -arg2"
).start();

Use this:

Process p = new ProcessBuilder(
    "C:\DoStuff.exe", "-arg1", "-arg2"
).start();

Alternatively, you can create a List and pass it to ProcessBuilder as follows:

List<String> params = Arrays.asList("C:\DoStuff.exe", "-arg1", "-arg2");
Process p = new ProcessBuilder(params).start();

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