Looping over files and directories in Bash Scripting - Step-by-Step Execution

Concept Flow - Looping over files and directories

Start

↓

Get list of files/directories

↓

For each item in list

↓

Process item

↓

More items?

Yes→Process next item

No↓

End

The script starts by getting a list of files and directories, then loops over each item to process it until all items are handled.

Execution Sample

Bash Scripting

for item in *; do
  echo "$item"
done

This script loops over all files and directories in the current folder and prints their names one by one.

Execution Table

Iteration	item value	Action	Output
1	file1.txt	echo "$item"	file1.txt
2	file2.txt	echo "$item"	file2.txt
3	dir1	echo "$item"	dir1
4	script.sh	echo "$item"	script.sh
5	image.png	echo "$item"	image.png
6		No more items	Loop ends

💡 All files and directories matched by * have been processed, loop ends.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
item	unset	file1.txt	file2.txt	dir1	script.sh	image.png	image.png

Key Moments - 3 Insights

Why does the loop stop after the last file is processed?

The loop stops because the glob * expands to all files and directories once. After the last item is processed (row 5 in execution_table), there are no more items to loop over, so the loop ends (row 6).

What happens if there are no files or directories in the folder?

If the folder is empty, the glob * expands to itself as a string '*', so the loop runs once with item='*'. This can be avoided by checking if the item is a real file or directory inside the loop.

Why do we use quotes around "$item" in echo?

Quotes ensure that if the filename has spaces or special characters, it is treated as a single string and printed correctly, avoiding word splitting or errors.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'item' at iteration 3?

A script.sh

B file2.txt

C dir1

D file1.txt

💡 Hint

Check the 'item value' column at iteration 3 in the execution_table.

At which iteration does the loop end because there are no more items?

A 6

B 4

C 5

D 7

💡 Hint

Look for the row in execution_table where the action says 'No more items'.

If the folder is empty, what will the loop variable 'item' be set to during the loop?

A empty string

B the string '*'

C null

D no loop runs

💡 Hint

Refer to the key_moments section about what happens when the folder is empty.

Concept Snapshot

Loop over files/directories using: for item in *; do ... done
The * expands to all files and folders in current directory.
Each item is processed one by one inside the loop.
Use quotes around "$item" to handle spaces.
Loop ends when all items are processed.

Full Transcript

This lesson shows how to loop over files and directories in bash using a for loop with the * wildcard. The * expands to all files and directories in the current folder. The loop variable 'item' takes each filename one by one. Inside the loop, we can run commands on each item, like echo to print its name. The loop stops after all items are processed. If the folder is empty, the loop runs once with item='*'. Using quotes around "$item" ensures filenames with spaces print correctly. This visual trace helps beginners see each step and variable change clearly.