Running with all permissions (--allow-all) in Deno - Mini Project: Build & Apply

Running a Deno Script with All Permissions

📖 Scenario: You want to run a Deno script that needs full access to your computer's resources, like reading files, accessing the network, and running subprocesses.

🎯 Goal: Learn how to run a Deno script using the --allow-all flag to grant all permissions safely and correctly.

📋 What You'll Learn

Create a simple Deno script file named app.ts with a console log message.

Define a variable to hold the Deno run command with the --allow-all flag.

Write the command to run the script with all permissions.

Complete the command to execute the script using the --allow-all flag.

💡 Why This Matters

🌍 Real World

Developers often need to run scripts that require access to files, network, or environment. Using --allow-all simplifies permission management during development.

💼 Career

Understanding how to manage permissions in Deno is important for secure and efficient scripting in modern JavaScript/TypeScript environments.

1

Create a Deno script file

Create a file named app.ts and write this exact line: console.log("Hello from Deno with all permissions!")

Deno

# Your code here

Hint

This script just prints a message to the console.

2

Define the Deno run command with permissions

Create a variable called runCommand and set it to the string "deno eval --allow-all console.log('Hello from child script with all permissions!')"

Deno

console.log("Hello from Deno with all permissions!")
# Your code here

Hint

This variable holds the command to run your script with all permissions.

3

Write the command to run the script

Add a line that uses Deno.run() with { cmd: ["deno", "eval", "--allow-all", "console.log('Hello from child script with all permissions!')"] } to run the script with all permissions

Deno

console.log("Hello from Deno with all permissions!")
const runCommand = "deno eval --allow-all console.log('Hello from child script with all permissions!')"
# Your code here

Hint

This runs the script with all permissions granted.

4

Complete the script execution

Add await process.status() to wait for the script to finish running

Deno

console.log("Hello from Deno with all permissions!")
const runCommand = "deno eval --allow-all console.log('Hello from child script with all permissions!')"
const process = Deno.run({ cmd: ["deno", "eval", "--allow-all", "console.log('Hello from child script with all permissions!')"] })
# Your code here

Hint

This waits for the script to finish before exiting.

Practice

1. What does the --allow-all flag do when running a Deno script?

easy

A. Gives the script full access to all system permissions

B. Restricts the script from accessing the network

C. Only allows reading files but no writing

D. Runs the script without any permissions

Solution

1. Step 1: Understand the purpose of --allow-all

   This flag grants all permissions to the Deno script, including file, network, environment, and more.

2. Step 2: Compare with other permission flags

   Other flags restrict permissions, but --allow-all removes all restrictions for convenience.

3. Final Answer:

   Gives the script full access to all system permissions -> Option A

4. Quick Check:

   --allow-all = full permissions [OK]

Hint: Remember: --allow-all means no permission limits [OK]

Common Mistakes:

• Thinking it restricts permissions
• Confusing it with --allow-read only
• Assuming it disables permissions

2. Which of the following is the correct way to run a Deno script named app.ts with all permissions?

easy

A. deno run app.ts --allow-all

B. deno run --allow-all app.ts

C. deno --allow-all run app.ts

D. deno run app.ts --allow-read

Solution

1. Step 1: Recall Deno command syntax

   The correct order is: deno run [flags] script.ts. Flags come before the script name.

2. Step 2: Identify the correct flag placement

   deno run --allow-all app.ts places --allow-all before app.ts, which is correct syntax.

3. Final Answer:

   deno run --allow-all app.ts -> Option B

4. Quick Check:

   Flags come before script name [OK]

Hint: Put flags right after 'run' before script name [OK]

Common Mistakes:

• Placing flags after script name
• Using wrong flag like --allow-read
• Mixing command order

3. Consider this Deno script read_file.ts that reads a file and prints its content:

const data = await Deno.readTextFile("secret.txt");
console.log(data);

What will happen if you run deno run read_file.ts without any permission flags?

medium

A. The script will throw a permission error

B. The script will print the file content successfully

C. The script will run but print nothing

D. The script will crash with a syntax error

Solution

1. Step 1: Understand default permission behavior

   Deno denies file system access by default unless explicitly allowed.

2. Step 2: Analyze running without --allow-read or --allow-all

   Running without permissions causes a runtime permission error when trying to read files.

3. Final Answer:

   The script will throw a permission error -> Option A

4. Quick Check:

   No permission flags = permission error [OK]

Hint: No flags means no file access, expect permission error [OK]

Common Mistakes:

• Assuming script runs without errors
• Confusing permission error with syntax error
• Thinking script prints empty output

4. You run the command deno run --allow-net app.ts but your script also needs to read files. What is the best fix to avoid permission errors?

medium

A. Remove --allow-net flag

B. Change the script to not read files

C. Run the script without any flags

D. Add --allow-read flag or use --allow-all

Solution

1. Step 1: Identify missing permission

   The script needs file read permission, but only network permission is given.

2. Step 2: Fix by adding correct permission flags

   Add --allow-read or use --allow-all to grant all permissions and avoid errors.

3. Final Answer:

   Add --allow-read flag or use --allow-all -> Option D

4. Quick Check:

   Missing permission? Add it or use --allow-all [OK]

Hint: Add needed flags or use --allow-all for all permissions [OK]

Common Mistakes:

• Removing needed flags
• Running without flags expecting no errors
• Ignoring permission errors

5. You have a Deno script that needs to read files, write logs, access environment variables, and make network requests. Which command is the safest way to run it without permission errors but limiting unnecessary access?

hard

A. deno run --allow-all script.ts

B. deno run script.ts

C. deno run --allow-read --allow-write --allow-env --allow-net script.ts

D. deno run --allow-net script.ts

Solution

1. Step 1: Identify required permissions

   The script needs read, write, environment, and network permissions.

2. Step 2: Choose the command granting only needed permissions

   deno run --allow-read --allow-write --allow-env --allow-net script.ts grants exactly those permissions, avoiding full access.

3. Step 3: Understand why --allow-all is less safe

   deno run --allow-all script.ts grants all permissions, which is less secure than specifying only needed ones.

4. Final Answer:

   deno run --allow-read --allow-write --allow-env --allow-net script.ts -> Option C

5. Quick Check:

   Grant only needed permissions, not all [OK]

Hint: Grant only needed permissions, avoid --allow-all if possible [OK]

Common Mistakes:

• Using --allow-all without need
• Running without permissions
• Granting too few permissions causing errors