[cli] Add prompt command for CLI logger. (#9897)

Co-authored-by: Richard Liaw <rliaw@berkeley.edu>

python/ray/autoscaler/cli_logger.py

@@ -550,7 +550,8 @@ class _CliLogger():
         confirm_str = cf.underlined("Confirm [" + yn_str + "]:") + " "
 
         rendered_message = _format_msg(msg, *args, **kwargs)
-        if rendered_message and rendered_message[-1] != "\n":
+        # the rendered message ends with ascii coding
+        if rendered_message and not msg.endswith("\n"):
             rendered_message += " "
 
         msg_len = len(rendered_message.split("\n")[-1])
@@ -602,6 +603,35 @@ class _CliLogger():
 
         return res
 
+    def prompt(self, msg: str, *args, **kwargs):
+        """Prompt the user for some text input.
+
+        Args:
+            msg (str): The mesage to display to the user before the prompt.
+
+        Returns:
+            The string entered by the user.
+        """
+        if self.old_style:
+            return
+
+        complete_str = cf.underlined(msg)
+        rendered_message = _format_msg(complete_str, *args, **kwargs)
+        # the rendered message ends with ascii coding
+        if rendered_message and not msg.endswith("\n"):
+            rendered_message += " "
+        self._print(rendered_message, linefeed=False)
+
+        res = ""
+        try:
+            ans = sys.stdin.readline()
+            ans = ans.lower()
+            res = ans.strip()
+        except KeyboardInterrupt:
+            self.newline()
+
+        return res
+
     def old_confirm(self, msg: str, yes: bool):
         """Old confirm dialog proxy.