Executable Scripts

Making Deno scripts executable can come in handy when creating small tools or utilities for tasks like file manipulation, data processing or repetitive tasks that you might want to run from the command line. Executable scripts allow you to create ad-hoc solutions without setting up an entire project.

Creating an example script Jump to heading#

To make a script executable, start the script with a hashbang, (sometimes called a shebang). This is a sequence of characters (#!) that tells your operating system how to execute a script. It is followed by the path to the interpreter that should be used to run the script.

We'll make a simple script that prints the Deno installation path using the Deno.env API.

Create a file named hashbang.ts with the following content:

#!/usr/bin/env -S deno run --allow-env
const path = Deno.env.get("DENO_INSTALL");

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

This script tells the system to use the deno runtime to run the script. The -S flag splits the command into arguments and indicates that the following argument (deno run --allow-env) should be passed to the env command.

The script then retrieves the value associated with the environment variable named DENO_INSTALL with Deno.env.get() and assigns it to a variable called path. Finally, it prints the path to the console using console.log().

Execute the script Jump to heading#

In order to execute the script, you may need to give the script execution permissions, you can do so using the chmod command with a +x flag (for execute):

chmod +x hashbang.ts

You can execute the script directly in the command line with:

./hashbang.ts

Using hashbang in files with no extension Jump to heading#

For brevity, you may wish to omit the extension for your script's filename. In this case, supply one using the --ext flag in the script itself, then you can run the script with just the file name:

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

🦕 Now you can directly execute Deno scripts from the command line! Remember to set the execute permission (chmod +x) for your script file, and you’re all set to build anything from simple utilities to complex tools. Check out the Deno examples for inspiration on what you can script.