Brace expansion ({1..10}) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the brace expansion {1..10} do in bash?

It generates a sequence of numbers from 1 to 10, expanding to 1 2 3 4 5 6 7 8 9 10.

beginner

How can you use brace expansion to create files named file1.txt to file10.txt?

Use the command touch file{1..10}.txt. This creates 10 files named file1.txt, file2.txt, ..., file10.txt.

intermediate

Can brace expansion generate sequences with steps, like every 2 numbers from 1 to 10?

Yes, by using {start..end..step}. For example, {1..10..2} expands to 1 3 5 7 9.

beginner

What happens if you use brace expansion with letters, like {a..e}?

It generates a sequence of letters from a to e: a b c d e.

intermediate

Is brace expansion performed before or after variable expansion in bash?

Brace expansion happens before variable expansion. So variables inside braces won't expand as part of the brace expansion.

What is the output of echo {3..7} in bash?

A 3..7

B {3..7}

C 3 4 5 6 7

D 7 6 5 4 3

Brace expansion generates the sequence 3 4 5 6 7.

Which command creates files named test1.txt to test5.txt using brace expansion?

A touch test[1-5].txt

B touch test{1..5}.txt

C touch test{1,5}.txt

D touch test1.txt test5.txt

The brace expansion {1..5} generates numbers 1 to 5 for file names.

How do you generate odd numbers from 1 to 9 using brace expansion?

A {1..9..2}

B {1..9..3}

C {1..9}

D {2..10..2}

Using a step of 2 with {1..9..2} generates 1 3 5 7 9.

What does echo {z..v} output?

A z y x w v

B v w x y z

C {z..v}

D Error

Brace expansion supports reverse sequences, so it outputs z y x w v.

If you run echo file{$i..10}.txt with i=3, what happens?

A Expands to file3.txt file4.txt ... file10.txt

B Outputs file3..10.txt

C Error because variable inside braces

D Outputs file{$i..10}.txt literally

Brace expansion happens before variable expansion, so $i is not expanded inside braces.

Explain how brace expansion works in bash using the example {1..10}.

Think about how you can quickly list numbers without typing each one.

Describe how to create multiple files named file1.txt to file10.txt using a single bash command.

Use brace expansion inside the file name.