diff --git a/lib/readline-sync.js b/lib/readline-sync.js
index aac2394..da7bcdf 100644
--- a/lib/readline-sync.js
+++ b/lib/readline-sync.js
@@ -35,7 +35,8 @@ var
     print:              void 0,
     history:            true,
     cd:                 false,
-    phContent:          void 0
+    phContent:          void 0,
+    preCheck:           void 0
   },
 
   fdR = 'none', fdW, ttyR, isRawMode = false,
@@ -494,6 +495,7 @@ function margeOptions() {
         // ================ function
         case 'print':                       // *    *
         case 'phContent':                   //      *
+        case 'preCheck':                    //      *
           options[optionName] = typeof value === 'function' ? value : void 0;
           break;
         // ================ other
@@ -662,14 +664,14 @@ function getPhCharlist(param) {
   return text;
 }
 
-// cmd "arg" " a r g " 'a"r"g' "a""rg" "arg
-function parseCL(cl) {
+// cmd "arg" " a r g " "" 'a"r"g' "a""rg" "arg
+function parseCl(cl) {
   var reToken = new RegExp(/(\s*)(?:("|')(.*?)(?:\2|$)|(\S+))/g), matches,
     taken = '', args = [], part;
   cl = cl.trim();
   while ((matches = reToken.exec(cl))) {
-    part = matches[3] || matches[4];
-    if (matches[1] && taken) {
+    part = matches[3] || matches[4] || '';
+    if (matches[1]) {
       args.push(taken);
       taken = '';
     }
@@ -679,9 +681,17 @@ function parseCL(cl) {
   return args;
 }
 
-function getValidLine(options, preCheck) {
-  var res, forceNext, resCheck, limitMessage,
-    matches, histInput, args;
+function toBool(res, options) {
+  return (
+    (options.trueValue.length &&
+      isMatched(res, options.trueValue, options.caseSensitive)) ? true :
+    (options.falseValue.length &&
+      isMatched(res, options.falseValue, options.caseSensitive)) ? false : res);
+}
+
+function getValidLine(options) {
+  var res, forceNext, limitMessage,
+    matches, histInput, args, resCheck;
   function _getPhContent(param) { return getPhContent(param, options); }
   function addDisplay(text)
     { options.display += (/[^\r\n]$/.test(options.display) ? '\n' : '') + text; }
@@ -715,8 +725,8 @@ function getValidLine(options, preCheck) {
       }
     }
 
-    if (options.cd && res) {
-      args = parseCL(res);
+    if (!forceNext && options.cd && res) {
+      args = parseCl(res);
       switch (args[0].toLowerCase()) {
         case 'cd':
           if (args[1]) {
@@ -737,8 +747,8 @@ function getValidLine(options, preCheck) {
       }
     }
 
-    if (preCheck) {
-      resCheck = preCheck(res, options);
+    if (!forceNext && options.preCheck) {
+      resCheck = options.preCheck(res, options);
       res = resCheck.res;
       if (resCheck.forceNext) { forceNext = true; } // Don't switch to false.
     }
@@ -756,14 +766,6 @@ function getValidLine(options, preCheck) {
   return toBool(res, options);
 }
 
-function toBool(res, options) {
-  return (
-    (options.trueValue.length &&
-      isMatched(res, options.trueValue, options.caseSensitive)) ? true :
-    (options.falseValue.length &&
-      isMatched(res, options.falseValue, options.caseSensitive)) ? false : res);
-}
-
 // for dev
 exports._DBG_set_useExt = function(val) { _DBG_useExt = val; };
 exports._DBG_set_checkOptions = function(val) { _DBG_checkOptions = val; };
@@ -1020,26 +1022,97 @@ exports.questionPath = function(query, options) {
   return validPath;
 };
 
-exports.promptSimShell = function(options) {
-  return exports.prompt(margeOptions({
+// props: preCheck, args, hRes, limit
+function getClHandler(commandHandler, options) {
+  var clHandler = {}, hIndex = {};
+  if (typeof commandHandler === 'object') {
+    Object.keys(commandHandler).forEach(function(cmd) {
+      if (typeof commandHandler[cmd] === 'function') {
+        hIndex[options.caseSensitive ? cmd : cmd.toLowerCase()] = commandHandler[cmd];
+      }
+    });
+    clHandler.preCheck = function(res) {
+      var cmdKey;
+      clHandler.args = parseCl(res);
+      cmdKey = clHandler.args[0] || '';
+      if (!options.caseSensitive) { cmdKey = cmdKey.toLowerCase(); }
+      clHandler.hRes =
+        hIndex.hasOwnProperty(cmdKey) ?
+          hIndex[cmdKey].apply(res, clHandler.args.slice(1)) :
+        hIndex.hasOwnProperty('_') ? hIndex._.apply(res, clHandler.args) : null;
+      return {res: res, forceNext: false};
+    };
+    if (!hIndex.hasOwnProperty('_')) {
+      clHandler.limit = function() { // It's called after preCheck.
+        var cmdKey = clHandler.args[0] || '';
+        if (!options.caseSensitive) { cmdKey = cmdKey.toLowerCase(); }
+        return hIndex.hasOwnProperty(cmdKey);
+      };
+    }
+  } else {
+    clHandler.preCheck = function(res) {
+      clHandler.args = parseCl(res);
+      clHandler.hRes = typeof commandHandler === 'function' ?
+        commandHandler.apply(res, clHandler.args) : null;
+      return {res: res, forceNext: false};
+    };
+  }
+  return clHandler;
+}
+
+exports.promptCL = function(commandHandler, options) {
+  var readOptions = margeOptions({
       // -------- default
       hideEchoBack:       false,
+      limitMessage:       'Requested command is not available.',
+      caseSensitive:      false,
       history:            true
-    }, options, {
+    }, options),
       // -------- forced
-      prompt:             (function() {
-        return IS_WIN ?
-          '${cwd}>' :
-          // 'user@host:cwd$ '
-          (process.env.USER || '') +
-          (process.env.HOSTNAME ?
-            '@' + process.env.HOSTNAME.replace(/\..*$/, '') : '') +
-          ':${cwdHome}$ ';
-      })()
-    }));
+      // trueValue, falseValue are don't work.
+      // preCheck, limit (by clHandler)
+    clHandler = getClHandler(commandHandler, readOptions);
+  readOptions.limit = clHandler.limit;
+  readOptions.preCheck = clHandler.preCheck;
+  exports.prompt(readOptions);
+  return clHandler.args;
 };
 
-exports.promptCL = function(options) {
+exports.promptLoop = function(inputHandler, options) {
+  var readOptions = margeOptions({
+      // -------- default
+      hideEchoBack:       false,
+      trueValue:          null,
+      falseValue:         null,
+      caseSensitive:      false,
+      history:            true
+    }, options);
+  while (true) { if (inputHandler(exports.prompt(readOptions))) { break; } }
+  return;
+};
+
+exports.promptCLLoop = function(commandHandler, options) {
+  var readOptions = margeOptions({
+      // -------- default
+      hideEchoBack:       false,
+      limitMessage:       'Requested command is not available.',
+      caseSensitive:      false,
+      history:            true
+    }, options),
+      // -------- forced
+      // trueValue, falseValue are don't work.
+      // preCheck, limit (by clHandler)
+    clHandler = getClHandler(commandHandler, readOptions);
+  readOptions.limit = clHandler.limit;
+  readOptions.preCheck = clHandler.preCheck;
+  while (true) {
+    exports.prompt(readOptions);
+    if (clHandler.hRes) { break; }
+  }
+  return;
+};
+
+exports.promptSimShell = function(options) {
   return exports.prompt(margeOptions({
       // -------- default
       hideEchoBack:       false,
@@ -1098,7 +1171,7 @@ exports.keyInPause = function(query, options) {
   return;
 };
 
-exports.keyInSelect = function(query, items, options) {
+exports.keyInSelect = function(items, query, options) {
   var readOptions = margeOptions({
       // -------- default
       hideEchoBack:       false