for

Iterate using a list form.

for variable in list; do
    commands
done

Iterate using C style.

for (( init; condition; update )); do
    commands
done

Combined with brace expansion.

for variable in {1..10}; do
    commands
done

Combined with a file glob.

for file in *.txt; do
    commands
done

Pattern	Description
for i in 1 2 3	Iterates over a space-separated list in order.
for i in {1..10}	Iterates over integers from 1 to 10.
for i in {1..10..2}	Iterates in steps of 2: 1, 3, 5, ...
for f in *.php	Iterates over .php files in the current directory.
for f in $(cmd)	Iterates over the output of a command, line by line.
for (( i=0; i<n; i++ ))	C-style counter loop.
break	Exits the loop early.
continue	Skips the current iteration and moves to the next.

Iterates over a space-separated list in order.

for_fruits.sh

#!/bin/bash
for fruit in apple banana cherry; do
    echo "Fruit: $fruit"
done

bash for_fruits.sh
Fruit: apple
Fruit: banana
Fruit: cherry

You can also enter a for loop directly in the terminal. After pressing Enter following do, a > prompt appears — this means input is still expected. Enter done to execute.

for fruit in apple banana cherry; do
    echo "Fruit: $fruit"
done
Fruit: apple
Fruit: banana
Fruit: cherry

Use brace expansion {1..9} to specify a numeric range.

multiply.sh

for i in {1..9}; do
    echo "3 × $i = $(( 3 * i ))"
done

bash multiply.sh
3 × 1 = 3
3 × 2 = 6
3 × 3 = 9
...
3 × 9 = 27

Use a C-style counter loop to calculate the sum from 1 to 100.

sum_100.sh

sum=0
for (( i=1; i<=100; i++ )); do
    (( sum += i ))
done
echo "Sum from 1 to 100: $sum"

bash sum_100.sh
Sum from 1 to 100: 5050

Use a file glob (wildcard) to process files in the current directory.

count_lines.sh

for f in *.php; do
    if [ -f "$f" ]; then
        echo "  $f ($(wc -l < "$f") lines)"
    fi
done

bash count_lines.sh
  index.php (120 lines)
  ajax.php (85 lines)

Use continue to skip even numbers, and break to stop the loop when 7 is reached.

skip_break.sh

for i in {1..10}; do
    if (( i % 2 == 0 )); then
        continue   # skip even numbers
    fi
    if (( i == 7 )); then
        break      # stop at 7
    fi
    echo "$i"
done

bash skip_break.sh
1
3
5

Expand array elements with "${colors[@]}" and iterate over them.

colors.sh

colors=("red" "green" "blue" "yellow")
for color in "${colors[@]}"; do
    echo "Color: $color"
done

bash colors.sh
Color: red
Color: green
Color: blue
Color: yellow

File globs ('*.php') can be used directly in a for loop, but using command substitution like 'for f in $(ls *.php)' can cause unexpected word splitting on filenames with spaces. Use globs directly for safety.

When processing a large number of files, piping find output to xargs is often more memory-efficient. For condition-based loops, use while / until.