Running with all permissions (--allow-all) in Deno - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

It grants the script permission to access all system resources like file system, network, environment variables, and more without restrictions.

beginner

Why should you be careful when using --allow-all in Deno?

Because it gives the script full access to your system, which can be risky if the code is untrusted or malicious.

beginner

How would you run a Deno script named app.ts with all permissions?

Use the command: deno run --allow-all app.ts

intermediate

What is a safer alternative to --allow-all when running Deno scripts?

Grant only the specific permissions your script needs, like --allow-read or --allow-net, instead of all permissions.

intermediate

Can you revoke permissions after starting a Deno script with --allow-all?

No, permissions are granted at start time and cannot be revoked while the script runs.

What does the --allow-all flag do in Deno?

A Grants only network access

B Denies all permissions to the script

C Grants all permissions to the script

D Runs the script without any permissions

The --allow-all flag gives the script full access to system resources.

Which command runs server.ts with all permissions?

A deno run server.ts

B deno run --allow-all server.ts

C deno run --allow-net server.ts

D deno run --allow-read server.ts

Only --allow-all grants all permissions.

Why avoid using --allow-all with untrusted code?

A It slows down the script

B It limits file access

C It disables network access

D It can expose your system to risks

Full permissions can let malicious code harm your system.

Can you remove permissions after starting a Deno script with --allow-all?

A No, permissions are fixed at start

B Yes, anytime during execution

C Only network permissions can be removed

D Only file permissions can be removed

Permissions are set when the script starts and cannot be changed later.

What is a better practice than using --allow-all?

A Grant only needed permissions explicitly

B Run scripts without Deno

C Use <code>--allow-all</code> always

D Use no permissions at all

Granting only necessary permissions improves security.

Explain what the --allow-all flag does in Deno and why it should be used carefully.

Think about what full access means for your computer.

Describe a safer way to manage permissions in Deno instead of using --allow-all.

Consider giving only what is necessary.

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