Alternative to java.lang.Runtime.exec() th

Question

I am calling java.lang.Runtime.exec(...) but this seems to accept the command lines as an array and I want to use a single string.

How can I do the same using a single string?

Answer 1

From the linked Javadocs:

envp - array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.

So just pass in null for the second parameter, and the environment will be inhereted.

Answer 2

If you pass null for the second paramter the current environment will be inherited.

If you want to modify the current environment, you can build it from System.getEnv() like this:

private static String[] getEnv() {
    Map<String, String> env = System.getenv();
    String[] envp = new String[env.size()];
    int i = 0;
    for (Map.Entry<String, String> e : env.entrySet()) {
        envp[i++] = e.getKey() + "=" + e.getValue();
    }
    return envp;
}

Update

You can check your Java path with System.out.println(System.getenv("PATH"));

If path is ok, then try it with

String[] commands = new String[] { "bash", "-c", "python foo/bar.py" };
Runtime.getRuntime().exec(commands, null, new File("/workingDir"));

Answer 3

Currently there is no way of calling a system command with a command line as a single string and be able to specify the current directory.

It seems that Java API is missing this basic feature :)

The workaround is to use the array version instead of string.

Answer 4

From the documentation:

envp - array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.

It sounds like you want to pass null for that argument.