hashbang.md

Making Scripts Executable With a Hashbang (Shebang)

Concepts

• Deno.env provides the environment variables.
• env runs a program in a modified environment.

Overview

Making Deno scripts executable can come in handy when creating small tools.

Note: Hashbangs do not work on Windows.

Example

In this program we give the context permission to access the environment variables and print the Deno installation path.

#!/usr/bin/env -S deno run --allow-env

/**
 *  hashbang.ts
 */

const path = Deno.env.get("DENO_INSTALL");

console.log("Deno Install Path:", path);

Permissions

You may require to give the script execution permissions.

Unix

chmod +x hashbang.ts

Execute

Start the script by calling it like any other command:

./hashbang.ts

Details

• A hashbang has to be placed in the first line.

• -S splits the command into arguments.

• End the file name in .ts for the script to be interpreted as TypeScript.

Using hashbang in files with no extension

You may wish to not use an extension for your script's filename. In this case, you can supply one by using the --ext flag:

$ cat my_script
#!/usr/bin/env -S deno run --allow-env --ext=js
console.log("Hello!");
$ ./my_script
Hello!