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Wildcards and Globbing

Wildcards and globbing allow you to work with multiple files using simple patterns instead of typing each filename individually. They are essential for Linux administration, shell scripting, DevOps automation, and production operations.

Learning Path

Linux Mastery → Module 2: Linux Command Line Essentials → Lesson 7

Difficulty: Beginner

Reading Time: 25 Minutes

Course Progress

Course: Linux Mastery

Module: Linux Command Line Essentials

Lesson: 7 of 10

What You'll Learn

After completing this lesson, you'll be able to:

  • Understand what wildcards are
  • Learn how Bash performs globbing
  • Use *, ?, and []
  • Match files using character ranges
  • Use brace expansion
  • Combine wildcard patterns
  • Use wildcards safely in production

Prerequisites

Before starting this lesson, complete:

  • Module 1 – Linux Fundamentals
  • Module 2 Lessons 1–6

Why Learn Wildcards?

Imagine you have thousands of files.

Instead of typing:

rm app1.log

rm app2.log

rm app3.log

rm app4.log

You simply type:

rm *.log

One command.

Thousands of files.

This is the power of wildcards.

What is Globbing?

Globbing is the process performed by the Bash shell to expand wildcard patterns into matching filenames.

Example:

You type:

ls *.txt

Bash converts it to:

ls notes.txt report.txt users.txt

before executing the command.

Notice:

The shell expands the pattern, not the ls command.

Common Wildcards

Wildcard Meaning
* Zero or more characters
? Exactly one character
[] Match one character from a set
{} Brace expansion
[a-z] Character range

The * Wildcard

Matches zero or more characters.

Example files:

notes.txt

report.txt

linux.txt

config.yaml

backup.log

Display all text files:

ls *.txt

Output:

linux.txt

notes.txt

report.txt

Display all log files.

ls *.log

Display every file.

ls *

The ? Wildcard

Matches exactly one character.

Example files:

a.txt

b.txt

ab.txt

abc.txt

Command:

ls ?.txt

Matches:

a.txt

b.txt

Does NOT match:

ab.txt

Character Sets

Use square brackets.

Example:

app1.log

app2.log

app3.log

app4.log

Command:

ls app[12].log

Output:

app1.log

app2.log

Character Ranges

Example:

ls file[1-5].txt

Matches:

file1.txt

file2.txt

file3.txt

file4.txt

file5.txt

Alphabet range:

ls [a-f]*

Matches:

apple.txt

config.txt

docker.txt

Negation

Exclude characters.

ls [!0-9]*

Matches files not starting with numbers.

Brace Expansion

Brace expansion is not globbing.

It generates multiple strings.

Example:

mkdir project{1,2,3}

Creates:

project1

project2

project3

Create files:

touch server{1..5}.log

Creates:

server1.log

server2.log

server3.log

server4.log

server5.log

Alphabet expansion:

touch file{A..E}.txt

Creates:

fileA.txt

fileB.txt

fileC.txt

fileD.txt

fileE.txt

Combining Wildcards

Example:

ls project*.txt

Matches:

project1.txt

project_backup.txt

project-final.txt

Another example:

ls server?.log

Matches:

server1.log

server2.log

server3.log

Does NOT match:

server10.log

Hidden Files

Remember:

*

does not match hidden files.

Hidden files begin with:

.

Display hidden files.

ls -a

Match hidden files.

ls .*

Using Wildcards with Commands

Copy all YAML files.

cp *.yaml backup/

Delete all log files.

rm *.log

Move all shell scripts.

mv *.sh scripts/

Count all text files.

wc -l *.txt

Preview Before Deleting

Never run:

rm *.log

without checking.

Preview first:

ls *.log

Then:

rm *.log

This simple habit prevents accidental deletions.

Wildcards vs Regular Expressions

Many beginners confuse them.

Wildcards Regular Expressions
Used by Shell Used by Programs
Expand filenames Match text patterns
*.txt .*\.txt
Simple More Powerful

We'll cover Regular Expressions later in the course.

Real Production Example

Backup Kubernetes YAML files.

cp *.yaml backup/

Delete old logs.

rm *.old

Archive reports.

tar -czf reports.tar.gz *.csv

Move certificates.

mv *.crt certificates/

Production Perspective

DevOps engineers frequently use wildcards.

Examples:

Docker:

docker cp *.sql database:/

Git:

git add *.yaml

Terraform:

ls *.tf

Kubernetes:

kubectl apply -f *.yaml

Automation becomes much easier with wildcard patterns.

Hands-on Lab

Task 1

Create a practice directory.

mkdir wildcard-lab

cd wildcard-lab

Task 2

Create files.

touch app.py

touch app.js

touch app.java

touch notes.txt

touch report.txt

touch server1.log

touch server2.log

touch config.yaml

Task 3

List text files.

ls *.txt

Task 4

List log files.

ls *.log

Task 5

Match single character.

ls server?.log

Task 6

Create multiple files.

touch backup{1..5}.sql

Task 7

List SQL files.

ls *.sql

Task 8

Create alphabet files.

touch demo{A..D}.txt

Task 9

Display only demo files.

ls demo*

Command Deep Dive

Pattern Description Example
* Any number of characters *.txt
? One character file?.txt
[] Character set file[12].txt
[a-z] Character range [a-f]*
[!a-z] Negation [!0-9]*
{} Brace expansion file{1..5}.txt

Production Troubleshooting Scenario

Scenario

A server contains:

app1.log

app2.log

app3.log

error.log

backup.tar.gz

config.yaml

config-old.yaml

deployment.yaml

Tasks:

  1. Display all YAML files.
  2. Display only application logs.
  3. Delete only backup files.
  4. Copy all YAML files to a backup directory.
  5. Display files beginning with "config".

Possible solutions:

ls *.yaml

ls app*.log

rm *.tar.gz

cp *.yaml backup/

ls config*

Mini Challenge

Create the following files.

project1.txt

project2.txt

project3.txt

server1.log

server2.log

server3.log

config.yaml

docker-compose.yml

deploy.sh

Now perform the following:

  • List all .txt files.
  • List all .log files.
  • Display only project1.txt to project3.txt.
  • List files beginning with server.
  • Create backup1 to backup5 directories using a single command.
  • Copy all YAML files into a new directory named configs.

Best Practices

  • Preview wildcard matches with ls before using destructive commands.
  • Use quotes when you want to prevent shell expansion.
  • Prefer specific patterns over broad ones.
  • Combine wildcards with other commands for automation.
  • Test wildcard commands in a lab before running them in production.

Common Mistakes

❌ Running:

✅ Use:

rm *

without checking the current directory.

Always verify first:

pwd

ls

❌ Assuming * matches hidden files.

✅ It does not.

Use:

ls -a

ls .*

❌ Confusing brace expansion with globbing.

✅ Brace expansion creates filenames.

Globbing matches existing filenames.

Interview Questions

Beginner

  1. What is a wildcard?
  2. What does * match?
  3. What does ? match?
  4. What is brace expansion?

Intermediate

  1. Explain globbing.
  2. Why is brace expansion different from globbing?
  3. How do you match files beginning with "config"?
  4. How do you match files ending with .yaml?

Architect Level

  1. How can wildcard misuse cause production incidents?
  2. Why should engineers preview wildcard matches before deleting files?
  3. How do wildcards simplify DevOps automation?

Summary

In this lesson, you learned:

  • Wildcards
  • Globbing
  • *
  • ?
  • Character sets
  • Character ranges
  • Brace expansion
  • Production-safe wildcard usage

Wildcards are one of the most powerful features of the Linux shell. Mastering them will help you work faster, write cleaner scripts, and automate repetitive tasks with confidence.

Key Takeaways

  • Bash performs wildcard expansion before executing commands.
  • * matches zero or more characters.
  • ? matches exactly one character.
  • [] matches characters from a specified set or range.
  • Brace expansion generates multiple filenames.
  • Always preview wildcard matches before performing destructive operations.

What's Next?

Command History

In the next lesson, you'll learn:

  • Standard Input (stdin)
  • Standard Output (stdout)
  • Standard Error (stderr)
  • >
  • >>
  • <
  • |
  • tee
  • Redirecting command output
  • Building powerful command pipelines