curl for HTTP requests in Linux CLI - Time & Space Complexity

Time Complexity: curl for HTTP requests

O(n)

Understanding Time Complexity

When using curl to make HTTP requests, it is helpful to understand how the time it takes grows as you make more requests or handle larger responses.

We want to know how the total work changes when the number or size of requests changes.

Scenario Under Consideration

Analyze the time complexity of the following curl command used in a script.

for url in $(cat urls.txt); do
  curl -s "$url" -o /dev/null
  echo "Fetched $url"
done
    

This script reads a list of URLs from a file and fetches each one silently, discarding the output.

Identify Repeating Operations

Look for repeated actions that take time.

• Primary operation: The curl command fetching each URL.
• How many times: Once for each URL in the list.

How Execution Grows With Input

As the number of URLs grows, the total time grows roughly in direct proportion.

Input Size (n)	Approx. Operations
10	10 HTTP requests
100	100 HTTP requests
1000	1000 HTTP requests

Pattern observation: Doubling the number of URLs doubles the total requests and time.

Final Time Complexity

Time Complexity: O(n)

This means the total time grows linearly with the number of URLs you fetch.

Common Mistake

[X] Wrong: "Fetching multiple URLs with curl happens instantly or all at once."

[OK] Correct: Each curl call waits for the server response before moving on, so time adds up with each request.

Interview Connect

Understanding how repeated commands like curl scale helps you write efficient scripts and shows you can think about performance in real tasks.

Self-Check

What if we used parallel curl requests instead of one after another? How would the time complexity change?