Add raw mode support to REPL for immediate key handling (Ctrl+L/Ctrl+C/Ctrl+D) and update README with usage notes

README.md

@@ -147,6 +147,10 @@ The interactive shell supports:
 
 See [examples/08_repl_guide.luash](examples/08_repl_guide.luash) for a comprehensive guide.
 
+Notes:
+- Raw terminal mode (immediate Ctrl+L/Ctrl+C/Ctrl+D) auto-enables when attached to a TTY.
+- Force enable/disable with `LUASH_RAW=1` or `LUASH_RAW=0`.
+
 ### Debug Mode
 ```bash
 LUASH_DEBUG=1 ./luash script.luash

luash

@@ -210,22 +210,96 @@ function start_repl()
       return s:match("^%s*(.-)%s*$")
   end
 
+  -- Raw mode (optional) for immediate key handling like Ctrl+L
+  local function detect_tty()
+      local r = os.execute("test -t 0 >/dev/null 2>&1")
+      if type(r) == "number" then return r == 0 end
+      return r == true
+  end
+  local env_raw = os.getenv("LUASH_RAW")
+  local raw_mode_enabled = (env_raw == "1") or (env_raw == nil and detect_tty())
+
+  local function set_raw_mode(enable)
+      if enable then
+          os.execute("stty -echo -icanon -isig min 1 time 0")
+      else
+          os.execute("stty sane")
+      end
+  end
+
+  local function raw_read_line(prompt)
+      io.write(prompt)
+      io.flush()
+      local buf = {}
+      while true do
+          local ch = io.read(1)
+          if not ch then
+              return nil
+          end
+          local b = string.byte(ch)
+          if b == 10 or b == 13 then -- Enter
+              io.write("\n")
+              return table.concat(buf)
+          elseif b == 12 then -- Ctrl+L
+              -- Clear screen and reprint banner + prompt + current buffer
+              repl.buffer = table.concat(buf)
+              io.write("\27[2J\27[H")
+              io.flush()
+              print("🚀 Luash Interactive Shell")
+              print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
+              print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
+              print("")
+              io.write(prompt)
+              io.write(repl.buffer)
+              io.flush()
+              -- Keep current input for usability, but allow immediate Ctrl+D by not forcing buf non-empty
+              -- buf remains as-is
+          elseif b == 3 then -- Ctrl+C
+              return "__CTRL_C__"
+          elseif b == 4 then -- Ctrl+D
+              -- Exit immediately (treat as EOF) regardless of current buffer state
+              return nil
+          elseif b == 127 or b == 8 then -- Backspace/Delete
+              if #buf > 0 then
+                  table.remove(buf)
+                  io.write("\b \b")
+                  io.flush()
+              end
+          else
+              table.insert(buf, ch)
+              io.write(ch)
+              io.flush()
+          end
+      end
+  end
+
   -- Main REPL loop
   print("🚀 Luash Interactive Shell")
   print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
   print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
   print("")
   
+  if raw_mode_enabled then set_raw_mode(true) end
+  local ok_loop, loop_err = pcall(function()
   while true do
       local prompt = repl.buffer == "" and "luash> " or "    >> "
-      io.write(prompt)
-      io.flush()
-      
-      -- Safely read a line; handle Ctrl+C gracefully
-      local ok, line = pcall(io.read, "*line")
-      if not ok then
-          print("\nInterrupted (Ctrl+C)")
-          break
+      local line
+      if raw_mode_enabled then
+          line = raw_read_line(prompt)
+          if line == "__CTRL_C__" then
+              print("\nInterrupted (Ctrl+C)")
+              break
+          end
+      else
+          io.write(prompt)
+          io.flush()
+          -- Safely read a line; handle Ctrl+C gracefully
+          local ok, l = pcall(io.read, "*line")
+          if not ok then
+              print("\nInterrupted (Ctrl+C)")
+              break
+          end
+          line = l
       end
       
       if not line then -- EOF (Ctrl+D)
@@ -233,8 +307,8 @@ function start_repl()
           break
       end
       
-      -- Handle Ctrl+L (form feed) to clear screen
-      if line:find(string.char(12), 1, true) then
+      -- Handle Ctrl+L (form feed) to clear screen in non-raw mode
+      if (not raw_mode_enabled) and line:find(string.char(12), 1, true) then
           repl.buffer = ""
           io.write("\27[2J\27[H") -- Clear screen and move cursor to top
           io.flush()
@@ -342,6 +416,12 @@ Multi-line input supported for functions, loops, etc.]])
       end
       ::continue::
   end
+  end)
+  if raw_mode_enabled then set_raw_mode(false) end
+  if not ok_loop then
+      if raw_mode_enabled then set_raw_mode(false) end
+      print("\nREPL error: " .. tostring(loop_err))
+  end
 end
 
 -- 1. Check for an input file or REPL mode
@@ -378,7 +458,7 @@ end
 
 -- Preprocessing functions
 local function process_env_vars(code)
-  local lines = {}
+local lines = {}
   for line in code:gmatch("([^\r\n]*)") do
     if not line:match("^%s*%-%-") then -- Skip comments