curl for HTTP requests in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this curl command?

You run this command in a terminal:

curl -s -o /dev/null -w "%{http_code}" https://httpbin.org/status/404

What will be the output?

Linux CLI

curl -s -o /dev/null -w "%{http_code}" https://httpbin.org/status/404

A No output

B 404

C Error: Not Found

D 200

💡 Hint

The -w option prints the HTTP status code. The URL returns a 404 status.

The command suppresses output (-s), discards body (-o /dev/null), and prints only the HTTP status code (-w "%{http_code}"). The URL returns 404, so output is '404'.

💻 Command Output

intermediate

What does this curl command output?

Consider this command:

curl -I https://example.com

What kind of output will it produce?

Linux CLI

curl -I https://example.com

A Only the HTTP status code

B Full HTML content of the page

C Only HTTP headers of the response

D An error message

💡 Hint

The -I option fetches headers only.

The -I option tells curl to fetch only the HTTP headers, not the body content.

📝 Syntax

advanced

Which curl command correctly sends JSON data with POST?

You want to send JSON data '{"name":"Alice"}' to https://api.example.com/users using POST. Which command is correct?

A curl -X POST -H "Content-Type: application/json" https://api.example.com/users

B curl -X POST -d '{"name":"Alice"}' -H "Content-Type: text/plain" https://api.example.com/users

C curl -X GET -H "Content-Type: application/json" -d '{"name":"Alice"}' https://api.example.com/users

D curl -X POST -H "Content-Type: application/json" -d '{"name":"Alice"}' https://api.example.com/users

💡 Hint

Use POST method, set content type to application/json, and provide data with -d.

Option D correctly uses POST, sets the header to application/json, and sends the JSON data with -d. Option D has wrong content type. Option D uses GET which ignores data. Option D sends no data.

🔧 Debug

advanced

Why does this curl command fail to send data?

This command is run:

curl -X POST https://api.example.com/data -d name=Bob&age=25

But the server reports only partial data received. Why?

Linux CLI

curl -X POST https://api.example.com/data -d name=Bob&age=25

A The -d option needs quotes around the data to be sent correctly

B POST method is not supported by curl

C The -X POST option must come after the URL

D The URL is missing a trailing slash

💡 Hint

Shell may split unquoted data into multiple arguments.

Without quotes, the shell splits name=Bob&age=25 into multiple parts due to the & operator, so curl sends incomplete data. Quoting the data keeps it as one argument.

🚀 Application

expert

How to save only HTTP response headers to a file using curl?

You want to save only the HTTP headers from https://example.com to a file named headers.txt, without saving the body. Which command does this?

A curl -s -D headers.txt -o /dev/null https://example.com

B curl -s -I https://example.com > headers.txt

C curl -s -o headers.txt -I https://example.com

D curl -s -o headers.txt https://example.com

💡 Hint

Use -D to save headers, -o /dev/null to discard body.

Option A saves headers to headers.txt (-D), discards body (-o /dev/null), and runs silently (-s). Option A saves headers to body file. Option A redirects headers to file but may include extra output. Option A saves full content.