How to send non-command data to the terminal from a JAVA program?

[mtrompe]

Hello,

I am working on a project where at one point, I have to login to an external program from my java program.
To do so, I have implemented the following function:

public void login(String password) throws IOException   
    {       
        //Send command to terminal   
        Process p = Runtime.getRuntime().exec("p4 login");   
           
        //Send password to terminal   
        p.getOutputStream().flush();   
        new PrintWriter(p.getOutputStream()).println(password);    
           
        //Read terminal output   
        Reader in = new InputStreamReader(p.getInputStream());   
        in = new BufferedReader(in);   
        char[] buffer = new char[20];   
        int len = in.read(buffer);   
        String s = new String(buffer, 0, len);   
           
        //Print for test   
        System.out.println(s);   
  
        //Test to know if user is logged in   
        if(s.startsWith("User")) loggedIn=true;   
        else loggedIn=false;   
        loggedIn=true;   
    }

This function successfully sends the "p4 login" function to the terminal, but apparently, the next command where I send the password does not work.
I know this because of the output I receive after the System.out.println(); Indeed, the output is always "Enter password", which is the anwser of the first command.

If anyone knows how to send a non-command data to the terminal, it would be great.

Thank you

[Norm]

how to send a non-command data to the terminal

Use the stream provided by the Process class.

Your code get two instances of the outputstream, try changing it to only get one and use that it the two places.

[mtrompe]

Use the stream provided by the Process class.

Your code get two instances of the outputstream, try changing it to only get one and use that it the two places.

I don't understand, I thought I already used the stream provided by the Process class with
new PrintWriter(p.getOutputStream()).println(password)

and also I don't understand why you say that I have two instances of the output stream because I only use it once (except for the flush)

I'm sorry there is not much that I understood in your response, don't hit too hard on me :p

[Norm]

Are there any messages on the error stream?

[mtrompe]

That I can not tell, when I try reading the error stream, the program starts loading and never stops

[Norm]

Sorry, I don't understand what "never stops" means. What program does that?

[mtrompe]

What I mean is that the program seems the be doing some stuff when I ask him to read the input, but he never sends anything

[Norm]

Are you sending the response before the process has asked for it?
Read the request first and then send the response.

[mtrompe]

I updated my code to:

public void login(String password) throws IOException
{
//Send command to terminal
Process p = Runtime.getRuntime().exec("p4 login");

//Read terminal output
Reader in = new InputStreamReader(p.getInputStream());
in = new BufferedReader(in);
char[] buffer = new char[4];
int len = in.read(buffer);
String s = new String(buffer, 0, len);
//Print for test
System.out.println(s);

//Send password to terminal
new PrintWriter(p.getOutputStream(),true).println(pass word);

//Read terminal output

in = new BufferedReader(in);
char[] buffer2 = new char[204];
int len2 = in.read();
String s2 = new String(buffer2, 0, len2);

//Print for test
if(s2!=null) System.out.println(s2);

//Test to know if user is logged in
if(s.startsWith("User")) loggedIn=true;
else loggedIn=false;
loggedIn=true;
}

so I read the output before sending the second request

[Norm]

Does it work now?

[mtrompe]

No, it prints "Enter password:" which is the response of the first request, but then it doesn't print anything, as if I never sent a second request

[Norm]

Why is the buffer only 4 char long?
What prints out for s and s2?
Try flushing what you write.
Try adding a newline at the end of what you write.

[mtrompe]

The size of the buffer does matter much. True, it is too small but doesn't affect the program.
s is the string in which I store the terminal output of the first request.
s2 is the string in which I store the terminal ouput of the second request.
I already tried adding a new line at the end of the password, but it doesn't change anything.
And I also flushed what I write, doesn't change anything.

[Norm]

Try a bigger buffer to make sure all is read from stream.
What prints out for s and s2? Post the output.

[mtrompe]

s = "Enter password:"
s2 = nothing

[Tolls]

You ought to show us the code with the flush after you have sent the password.
The lack of a flush there would concern me that it is simply stuck in the buffer.

[Norm]

The size of the buffer does matter much.

How is s longer than 4 characters? Your code shows a 4 char buffer???

[mtrompe]

Sorry, I put 4 in the buffer just to test something.
It is actually at 20

[Norm]

Please post the code that you are now working with.

[DarrylBurke]

I updated my code to:

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