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Making Scripts Executable With a Hashbang (Shebang)

Concepts​

  • Deno.env provides 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 need 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 not wish to use an extension for your script's filename. In this case supply one using the --ext flag.

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