How to provide input selection in shell script when running though Java program?

Question

In my Java program what I am trying to do is:

First, I connect to a Unix server and execute one shell script. But in that shell script, you have to select the option to perform the different operation once the option is selected.

For example:

Please select from below menu options
1. Create directory and subdirectory
2. Copy files
3. Update paths
4. Press 9 to exit

Here each option performs different operations and upon selecting any asks for further input. For ex: If I select an option 1 it will ask for the path:

Please enter the path where you want to create a directory

Now my question is: How can I enter this input while running this shell script from Java code?

Below code is written For connecting to unix server and execution of shell script:

JSch jsch = new JSch();

String command = "/tmp/myscript.sh";
Session session = jsch.getSession(user, host, 22);
session.connect();

Channel channel = session.openChannel("exec");
((ChannelExec)channel).setCommand(command);

channel.setInputStream(null);
((ChannelExec)channel).setErrStream(System.err);
InputStream in = channel.getInputStream();
java.util.Properties config = new java.util.Properties();
config.put("StrictHostKeyChecking", "no");
channel.connect();

byte[] tmp = new byte[1024];
while (true) {
  while (in.available() > 0) {
      int i = in.read(tmp, 0, 1024);
      if (i < 0) {
          break;
      }
      System.out.print(new String(tmp, 0, i));
  }
  if (channel.isClosed()) {
      if (channel.getExitStatus() == 0) {
          System.out.println("Command executed successully.");
      }
      break;
  }
}
channel.disconnect();
session.disconnect();

How do you want to get the input? A GUI? Something custom from your program? stdin (of your program)? In the last case, you could try channel.setInputStream(System.in);. — dan1st
– dan1st, Commented May 26, 2021 at 19:10
Why are you reading from your channel's input stream instead of writing to it? — Charles Duffy
– Charles Duffy, Commented May 26, 2021 at 19:11
BTW, it would be a better minimal reproducible example if instead of depending on a myscript.sh nobody but you has, you executed something like String[]{"bash", "-c", "read -p 'need input: ' input; echo \"got input: $input\""} -- that way your code wouldn't require dependencies it doesn't contain. — Charles Duffy
– Charles Duffy, Commented May 26, 2021 at 19:13
likely you can't, using shell select creates a interactive shell and holds stdin, and you are still try to glue back with java, why ? haha — Jack Wu
– Jack Wu, Commented Jun 1, 2021 at 13:13

Tigger · Accepted Answer · 2021-06-01 15:59:11Z

Let's say we want to "Create directory and subdirectory", then exit.
Once the channel is ready, we have to:

send create command "1"
send path "/path/to/directory"
send exit command "9"

JSch jsch = new JSch();

String command = "/tmp/myscript.sh";
Session session = jsch.getSession(user, host, 22);
session.setConfig("StrictHostKeyChecking", "no");
session.setPassword(passwd);
session.connect();

ChannelExec channel = (ChannelExec) session.openChannel("exec");
channel.setCommand(command);
channel.setInputStream(null);
channel.setErrStream(System.err);
InputStream is = channel.getInputStream();
// We will send commands through this stream
OutputStream os = channel.getOutputStream();
channel.connect();

int step = 1;
byte[] tmp = new byte[1024];
int read;
while (true) {
    // Wait for available data
    while(is.available() == 0) {
        Thread.sleep(100);
    }
    // Read the script/command output
    while(is.available() > 0) {
        read = is.read(tmp);
        if (read < 0) {
            break;
        }
        System.out.print(new String(tmp, 0, read));
    }
    // Send a command depending on current step
    switch(step) {
    case 1:
        // 1. Create directory command
        os.write("1\n".getBytes());
        os.flush();
        break;
    case 2:
        // 2. Path to create
        os.write("/path/to/directory\n".getBytes());
        os.flush();
        break;
    case 3:
        // 3. Exit command
        os.write("9\n".getBytes());
        os.flush();
        break;
    }
    step++;
    if (channel.isClosed()) {
        if (channel.getExitStatus() == 0) {
            System.out.println("Command executed successully.");
        }
        break;
    }
}
channel.disconnect();
session.disconnect();

The final "\n" and a call to os.flush are mandatory for each command.

HappyFace · Accepted Answer · 2021-05-27 21:34:13Z

0

You can probably get away with printing to /dev/tty and reading from /dev/tty in your shell script. Wrap /tmp/myscript.sh like so:

#!/bin/bash
(
ORIGINAL_CODE_HERE
) < /dev/tty > /dev/tty

answered May 27, 2021 at 21:34

HappyFace

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