{} (Brace Expansion)

Expand comma-separated values.

{a,b,c}

Sequence of integers.

{start..end}
{start..end..step}

Sequence of characters.

{a..z}
{A..Z}

Combine with a prefix and/or suffix.

prefix{a,b,c}suffix

Nested braces are also supported.

{a,{b,c},d}

Expansion	Example result	Description
{a,b,c}	a b c	Expands comma-separated strings.
{1..5}	1 2 3 4 5	Expands a sequence of integers.
{1..10..2}	1 3 5 7 9	Expands integers with a step value.
{a..e}	a b c d e	Expands a sequence of alphabet characters.
file{1..3}.txt	file1.txt file2.txt file3.txt	Expands with a prefix and suffix attached.
{01..05}	01 02 03 04 05	Expands with zero-padding.
{a,b}{1,2}	a1 a2 b1 b2	Combines multiple braces to generate all combinations.

Basic comma expansion.

echo {apple,banana,cherry}
apple banana cherry

Expanding a sequence of integers.

echo {1..5}
1 2 3 4 5

Expanding with a step value.

echo {0..20..5}
0 5 10 15 20

You can also expand in reverse order.

echo {5..1}
5 4 3 2 1

Expanding a sequence of alphabet characters.

echo {a..f}
a b c d e f

Useful for creating multiple files or directories at once.

touch report_{2023,2024,2025}.txt
ls report_*.txt
report_2023.txt  report_2024.txt  report_2025.txt

mkdir -p project/{src,tests,docs,build}
ls project/
build  docs  src  tests

The {,.bak} expansion trick creates a backup of a file. Because the first element is an empty string, this is equivalent to cp config.json config.json.bak.

cp config.json{,.bak}

Expanding with zero-padding.

echo {01..05}
01 02 03 04 05

Combining with a for loop.

deploy.sh

for env in {dev,staging,prod}; do
    echo "Deploying to: $env"
done

bash deploy.sh
Deploying to: dev
Deploying to: staging
Deploying to: prod

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

for env in {dev,staging,prod}; do
    echo "Deploying to: $env"
done
Deploying to: dev
Deploying to: staging
Deploying to: prod

Combining multiple braces generates all combinations (the Cartesian product).

echo {A,B}{1,2,3}
A1 A2 A3 B1 B2 B3

Brace expansion is processed first in the shell's expansion order. Keep this in mind when using variables inside braces — for example, {1..$n} does not work, because variables are expanded after brace expansion. To use a variable as a range, use the $ seq command or a C-style loop inside a for loop.

The zero-width expansion trick, such as cp file{,.bak}, is handy for creating file backups. It works because the first element of {,} is an empty string.