Running scripts in Bash Scripting - Time & Space Complexity

Time Complexity: Running scripts

O(n)

Understanding Time Complexity

When we run a script, we want to know how long it takes as the work grows.

We ask: How does running time change when the script handles more data or commands?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

#!/bin/bash

for file in /path/to/folder/*; do
  echo "Processing $file"
  grep "pattern" "$file"
done

This script lists files in a folder and searches each file for a pattern.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Looping over each file in the folder.
• How many times: Once for each file found in the folder.

How Execution Grows With Input

As the number of files grows, the script runs the loop more times.

Input Size (n)	Approx. Operations
10	10 times running grep
100	100 times running grep
1000	1000 times running grep

Pattern observation: The work grows directly with the number of files.

Final Time Complexity

Time Complexity: O(n)

This means the running time grows in a straight line as the number of files increases.

Common Mistake

[X] Wrong: "Running the script takes the same time no matter how many files there are."

[OK] Correct: Each file adds more work because the script processes them one by one.

Interview Connect

Understanding how script running time grows helps you explain your code's efficiency clearly and confidently.

Self-Check

"What if we changed the script to process files in parallel? How would the time complexity change?"