Making scripts executable (chmod +x) in Bash Scripting - Time & Space Complexity

Time Complexity: Making scripts executable (chmod +x)

O(n)

Understanding Time Complexity

Let's explore how the time it takes to make a script executable changes as the number of scripts grows.

We want to know how the work increases when we use chmod +x on many files.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

for file in *.sh; do
  chmod +x "$file"
done
    

This script loops over all files ending with .sh and makes each one executable.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The chmod +x command inside the loop.
• How many times: Once for each .sh file found.

How Execution Grows With Input

As the number of script files grows, the total time grows in a similar way.

Input Size (n)	Approx. Operations
10	10 times running chmod +x
100	100 times running chmod +x
1000	1000 times running chmod +x

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

Final Time Complexity

Time Complexity: O(n)

This means the time to make scripts executable grows linearly with the number of files.

Common Mistake

[X] Wrong: "Running chmod +x on many files takes the same time as on one file."

[OK] Correct: Each file needs its own permission change, so more files mean more time.

Interview Connect

Understanding how simple loops affect execution time helps you explain script performance clearly and confidently.

Self-Check

"What if we used a single chmod +x *.sh command instead of a loop? How would the time complexity change?"