Runtime.exec() under a specific user account ???

Question

Hi there,
I cann't figure out how to run a script on Unix under a specific user account using the Runtime.exec(). Currently whoever run the java program, the script is ran under that user account.
The code is like:
public class javarun {
public static void main(String[] arg) {
String str = "myunixscript";
// check the arg[1] to decide the appropriate environment.
Runtime r = Runtime.getRuntime();
try {
Process pr = r.exec(str);
pr.waitFor();
int exitstatus = pr.exitValue();
} catch (...) {...}
We have two user accounts: unixusr1 and unixusr2. Now I need to have unixusr1 run the java program ( ie. unixusr1$ java javarun), while the "myunixscript" be executed under unixusr2. One further step is to the unix account name as a parameter so the unixscript could be run under different account.
Any help will be highly appreciated. Thanks.
Edward.

Answer 1

I'm not sure if I have a solution, but here are some questions:
a) have you tried writing additional input to the OutputStream of the process? Although I have not tried it, I would imagine that Process.getOutputStream() exists for commands that require the invoking resource to send additional input to the process- like an su command that requires a password check.
b) can you just write a shell script that takes the needed information as an argument. That is, write a shell script that takes the username and password as an argument and then you can use Runtime like,
Runtime.exec("myScript", new String[] { "hisId", "hisPasswd" });Obviously, you would need to think through the security concerns of such a script, but, if it complies with the security structure of your environment, it might allow you to avoid the problem by using the shell script to invoke the destination command with the proper UID and password, rather then using the JVM to invoke it. Basically, the script becomes a proxy for the JVM to invoke that command.