C#. Unity. System.Diagnostics library. Spawn system processes, TMP_InputField and TMP_Text. Mock Terminal.

Terminal.cs

using System.Diagnostics;
using System.IO;
using System.Threading;
using TMPro;
using UnityEngine;

public class Terminal : MonoBehaviour
{
    public TMP_InputField inputField;
    public TMP_Text outputText;
    public TMP_Text outputTextCurrentDirectory;
    public TMP_Text outputTextCommandEntered;

    private string currentDirectory = Directory.GetCurrentDirectory();

    private Process process;
    private SynchronizationContext mainThreadContext;

    private Process processToKill;

    private void Awake()
    {
        mainThreadContext = SynchronizationContext.Current;
    }

    private void Start()
    {
        inputField.onEndEdit.AddListener(SendCommand);
        outputTextCurrentDirectory.text = currentDirectory;
    }

    private void Update()
    {
        if (Input.GetKey(KeyCode.LeftControl) && Input.GetKeyDown(KeyCode.C))
        {
            // Plus 1 hack...
            string killCommand = "kill " + (processToKill.Id + 1);
            SendCommand(killCommand);
            mainThreadContext.Post(_ => outputTextCommandEntered.text += "\n" + killCommand, null);
        }
    }

    private void SendCommand(string command)
    {
        Thread thread = new(() =>
        {
            process = new Process();
            processToKill = process;

            // Handle directory changes
            if (command.Split(' ')[0] == "cd")
            {
                currentDirectory = command[3..];
                print("Changing directory to: " + currentDirectory);
                mainThreadContext.Post(_ => outputTextCurrentDirectory.text = currentDirectory, null);
                mainThreadContext.Post(_ => inputField.text = "", null);
            }

            process.StartInfo.FileName = "/bin/bash";
            process.StartInfo.Arguments = "-c \"cd " + currentDirectory + " && " + command + "\"";
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardOutput = true;
            process.StartInfo.RedirectStandardError = true;

            process.OutputDataReceived += (sender, args) =>
            {
                if (args.Data != null)
                {
                    mainThreadContext.Post(_ => outputText.text += "\n" + args.Data, null);
                    mainThreadContext.Post(_ => outputTextCurrentDirectory.text = currentDirectory, null);
                    mainThreadContext.Post(_ => inputField.text = "", null);
                    mainThreadContext.Post(_ => outputTextCommandEntered.text += "\n" + command + " " + process.Id, null);
                }
            };

            process.ErrorDataReceived += (sender, args) =>
            {
                if (args.Data != null)
                {
                    mainThreadContext.Post(_ => outputText.text += "\n" + args.Data, null);
                    mainThreadContext.Post(_ => outputTextCurrentDirectory.text = currentDirectory, null);
                    mainThreadContext.Post(_ => inputField.text = "", null);
                    mainThreadContext.Post(_ => outputTextCommandEntered.text += "\n" + command + " " + process.Id, null);
                }
            };

            process.Start();
            process.BeginOutputReadLine();
            process.BeginErrorReadLine();
            process.WaitForExit();
        });

        thread.Start();
    }
}

Todo:

• - IO stream handling for commands like ping or top.

• - Keyboard interupt handlers; ctrl-c for instance.

• - Clear input field "On End Edit", eg. when user hits enter.

• - Handle directory changes, eg. "cd ~/"

• - Fix the way user input is parsed. A command like echo "foo" > bar breaks command call.

• - Backround image and green text, because its kewl.

all items complete