can I change user password in linux from java program?

Question

I am trying to change user password in linux from java program by sending password in outputstream but it is not done.

My java program is like

Process process = Runtime.getRuntime().exec("sudo passwd sampleuser");

OutputStream outputStream = process.getOutputStream();

InputStream inputStream = process.getInputStream();

PrintWriter printWriter=new PrintWriter(outputStream);

printWriter.write("123456");

printWriter.write("\n");

printWriter.flush();

My program fails here and it ask for password but I does not want this case.

Is there any possibility for providing password from java program ? can you suggest me,how I will do it successfully or is there any shell api's available for it.

Same thing is done successful when I try using shell script and calling it from my java program as

Process process = Runtime.getRuntime().exec("bash first.sh");

My shell script is

i="123456"

echo -e $i"\n"$i|sudo -S passwd sampleuser

It changes user password successfully.

Kazekage Gaara · Accepted Answer · 2012-06-01 07:58:00Z

5

It will ask for password. Look at your shell script. You execute a command that asks for super user privileges(sudo). Your program will prompt for a password unless you run it as a super user.

To break down your shell script:

i="123456"

echo -e $i"\n"$i|sudo -S passwd sampleuser

sudo -S means :

The -S (stdin) option causes sudo to read the password from the standard input instead of the terminal device. The password must be followed by a newline character.

And that is what your script is doing, it is setting password(passwd) for your sampleuser as i. And since you are using -S it is reading from the standard input,to which you have already given your variable i. And you are doing all this as a super user! keep that in mind.

Now look back at your java program and try for the changes accordingly. Do you have super user privileges when you run your program? No,you don't.

edited Jun 1, 2012 at 7:58

answered Jun 1, 2012 at 7:39

Kazekage Gaara

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2 Comments

tom Over a year ago

"Do you have super user privileges when you run your program? I guess not." --> I really hope not.

Kazekage Gaara Over a year ago

Exactly! I better edit that line to make better sense out of it.

BoltClock · Accepted Answer · 2012-06-01 15:18:56Z

0

I'm not sure why your approach fails. I suppose passwd uses a different stream.

But use ExpectJ for this. It is made just for such cases.

edited Jun 1, 2012 at 15:18

BoltClock

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answered Jun 1, 2012 at 7:44

bdecaf

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Comments

user3498865 · Accepted Answer · 2017-05-18 14:11:06Z

0

If someone is looking for an answer, I just find a way with this lines :

try {
    Process p = Runtime.getRuntime().exec(new String[] {"sudo", "/bin/sh", "-c", "echo \"user:newpassword\" | sudo chpasswd"} );
    p.waitFor();
} catch (IOException | InterruptedException e1) {
    e1.printStackTrace();
}

answered May 18, 2017 at 14:11

user3498865

1

1 Comment

Reporter Over a year ago

Please add an explanation for your intention. This might be help the questionoer and further visitors either. You can doing that by click on the edit link underneath your post.

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