diff --git a/tools/rbcrun/cmd/rbcrun.go b/tools/rbcrun/cmd/rbcrun.go
new file mode 100644
index 0000000..7848562
--- /dev/null
+++ b/tools/rbcrun/cmd/rbcrun.go
@@ -0,0 +1,98 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"go.starlark.net/starlark"
+	"os"
+	"rbcrun"
+	"strings"
+)
+
+var (
+	execprog = flag.String("c", "", "execute program `prog`")
+	rootdir  = flag.String("d", ".", "the value of // for load paths")
+	file     = flag.String("f", "", "file to execute")
+	perfFile = flag.String("perf", "", "save performance data")
+)
+
+func main() {
+	flag.Parse()
+	filename := *file
+	var src interface{}
+	var env []string
+
+	rc := 0
+	for _, arg := range flag.Args() {
+		if strings.Contains(arg, "=") {
+			env = append(env, arg)
+		} else if filename == "" {
+			filename = arg
+		} else {
+			quit("only one file can be executed\n")
+		}
+	}
+	if *execprog != "" {
+		if filename != "" {
+			quit("either -c or file name should be present\n")
+		}
+		filename = "<cmdline>"
+		src = *execprog
+	}
+	if filename == "" {
+		if len(env) > 0 {
+			fmt.Fprintln(os.Stderr,
+				"no file to run -- if your file's name contains '=', use -f to specify it")
+		}
+		flag.Usage()
+		os.Exit(1)
+	}
+	if stat, err := os.Stat(*rootdir); os.IsNotExist(err) || !stat.IsDir() {
+		quit("%s is not a directory\n", *rootdir)
+	}
+	if *perfFile != "" {
+		pprof, err := os.Create(*perfFile)
+		if err != nil {
+			quit("%s: err", *perfFile)
+		}
+		defer pprof.Close()
+		if err := starlark.StartProfile(pprof); err != nil {
+			quit("%s\n", err)
+		}
+	}
+	rbcrun.LoadPathRoot = *rootdir
+	err := rbcrun.Run(filename, src, env)
+	if *perfFile != "" {
+		if err2 := starlark.StopProfile(); err2 != nil {
+			fmt.Fprintln(os.Stderr, err2)
+			rc = 1
+		}
+	}
+	if err != nil {
+		if evalErr, ok := err.(*starlark.EvalError); ok {
+			quit("%s\n", evalErr.Backtrace())
+		} else {
+			quit("%s\n", err)
+		}
+	}
+	os.Exit(rc)
+}
+
+func quit(format string, s ...interface{}) {
+	fmt.Fprintln(os.Stderr, format, s)
+	os.Exit(2)
+}