Loops

Repeating Commands

Shell loops let you run commands multiple times — over a list of values, over files, or until a condition changes.

The for Loop

The most common loop iterates over a list:

for i in 1 2 3; do
  echo "Number $i"
done

Output:

Number 1
Number 2
Number 3

Structure:

• for VARIABLE in LIST; do — starts the loop
• COMMANDS — body (can be multiple lines)
• done — ends the loop

The variable (i) takes each value from the list in turn.

Iterating Over Files

for file in *.txt; do
  echo "Found: $file"
done

The *.txt glob expands to all .txt files in the current directory.

Iterating Over a Range

for i in $(seq 1 5); do
  echo "$i"
done

Or with brace expansion (bash):

for i in {1..5}; do
  echo "$i"
done

The while Loop

while runs as long as a condition is true:

COUNT=1
while [ $COUNT -le 3 ]; do
  echo "Count: $COUNT"
  COUNT=$((COUNT + 1))
done

Your Task

Write a for loop that prints Number 1, Number 2, and Number 3 on separate lines.