diff --git a/Cargo.lock b/Cargo.lock
index 079907e..145b937 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -128,7 +128,7 @@ dependencies = [
 
 [[package]]
 name = "runrs"
-version = "0.1.7"
+version = "0.1.8"
 dependencies = [
  "rust_util",
  "sha256",
diff --git a/Cargo.toml b/Cargo.toml
index e4939e7..e716d0f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "runrs"
-version = "0.1.7"
+version = "0.1.8"
 edition = "2018"
 license = "MIT/Apache-2.0"
 description = "Run Rust Scripts"
diff --git a/README.md b/README.md
index a3dbaed..647440f 100644
--- a/README.md
+++ b/README.md
@@ -3,8 +3,19 @@
 Run rust script
 
 Install:
+
 ```shell
 cargo install --git https://git.hatter.ink/hatter/runrs runrs
 ```
 
+Environment variables
+
+| KEY | value                                                         |
+| ---- |---------------------------------------------------------------|
+| `HOME` | User home, default by OS system                               |
+| `SKIP_CACHE` | Skip compiled cache file , turn on `true`, `yes`, `on` or `1` |
+| `RUST_SCRIPT` | `rust_script` command line bin file                           |
+
+<br>
+
 Simply call `rust-script` (https://github.com/fornwall/rust-script).
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e871767..d43264d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -19,17 +19,13 @@ fn main() {
         );
     }
     let first_argument = args.get(0).unwrap_or_else(|| failure_and_exit!("Must assign file name"));
-
     if first_argument == "--help" {
         print_help();
         return;
     }
-
     let script_file = first_argument;
-    let script_content = fs::read_to_string(script_file).unwrap_or_else(|e|
-        failure_and_exit!("Read file: {}, failed: {}", script_file, e)
-    );
-    let script_sha256 = sha256::digest(script_content);
+
+    let (_, script_sha256) = read_file_and_digest(script_file);
     debugging!("File {} -> sha256: {}", script_file, script_sha256);
     let cache_script_bin_name = format!("{}/Library/Caches/rust-script/binaries/release/{}",
                                         home,
@@ -86,7 +82,31 @@ runrs <script.rs> [arguments]
     );
 }
 
+fn read_file_and_digest(script_file: &str) -> (String, String) {
+    match fs::metadata(script_file) {
+        Err(_) => failure_and_exit!("Script file not exists: {}", script_file),
+        Ok(metadata) => if metadata.is_dir() {
+            failure_and_exit!("Assigned input is dir: {}", script_file);
+        } else if metadata.len() > 1024 * 1024 {
+            failure_and_exit!("Script file: {} too large: {}", script_file, metadata.len());
+        }
+    }
+    let script_content = fs::read_to_string(script_file).unwrap_or_else(|e|
+        failure_and_exit!("Read file: {}, failed: {}", script_file, e)
+    );
+    let script_sha256 = sha256::digest(&script_content);
+
+    (script_content, script_sha256)
+}
+
 fn get_run_script_bin_name(home: &str) -> PathBuf {
+    if let Ok(rust_script) = env::var("RUST_SCRIPT") {
+        let rust_script_path_buf = PathBuf::from(&rust_script);
+        if !rust_script_path_buf.exists() {
+            warning!("RUST_SCRIPT={} not exists", &rust_script);
+        }
+        return rust_script_path_buf;
+    }
     let rust_script = PathBuf::from(format!("{}/.cargo/bin/rust-script", home));
     if !rust_script.exists() {
         warning!("rust-script not found, install it...");
@@ -105,7 +125,7 @@ fn get_run_script_bin_name(home: &str) -> PathBuf {
 
 fn is_env_on(env: &str) -> bool {
     env::var(env).map(|v| {
-        let v = v.to_string();
+        let v = v.to_lowercase();
         v == "true" || v == "on" || v == "yes" || v == "1"
     }).unwrap_or_else(|_| false)
 }