Globbing and Wildcards

By the end of this lesson you'll be able to match many files at once with the shell's wildcards — * , ? , and bracket sets — generate names with brace expansion, recurse with ** , expand ~ to your home directory, and know exactly when to quote a pattern so the shell leaves it alone.

Learn Globbing and Wildcards in our free Command Line course — an interactive lesson with worked examples, a practice exercise and a quick reference.

Part of the free Cli course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

What You'll Learn

1. Set Up a Predictable Sandbox

Globbing matches the files that actually exist, so to get the same output every time we first create a known set of files. Run this once; every later example assumes you're inside this globdemo folder.

2. The * Wildcard: Any Run of Characters

* matches any sequence of characters (including an empty one) within a single filename. Two rules trip people up: a bare * does not match files that begin with a dot (so .hidden is skipped), and * does not cross the / between directories — it stays inside one folder.

3. The ? Wildcard: Exactly One Character

? matches exactly one character — no more, no less. That's the difference between file?.txt (matches file1.txt ) and file??.txt (matches file10.txt ). Use one ? per character you want to leave flexible.

4. Bracket Sets [abc] and Ranges [a-z]

A bracket expression [...] matches exactly one character from the listed set. List choices explicitly with [12] , or give a range with a hyphen like [1-5] or [a-z] . As always, a glob only lists files that truly exist, so a range that matches nothing is passed through literally.

5. Negating a Set with [!...]

Put ! (or ^ ) as the first character inside the brackets to match a single character that is not in the set. So [!1] matches one character that isn't 1 , and [!0-9] matches one non-digit character. Both ! and ^ work in bash.

6. Brace Expansion {a,b} and {1..10} — Not Globbing!

Brace expansion is not globbing. The shell generates strings from the braces before any filename matching, so echo file {1,2,3} .txt prints all three names whether or not the files exist . A real glob like file[1-3].txt only shows files that exist. They combine nicely: the shell expands the braces first, then matches the results as globs.

7. Globstar, Tilde, Quoting, and nullglob

Four power features. ** matches across subdirectories, but only after shopt -s globstar . ~ expands to your home directory (the value of $HOME ). Quoting or escaping a pattern ( "*.txt" or \*.txt ) disables globbing so the literal text is passed along. And by default a glob that matches nothing is left literal — shopt -s nullglob makes it expand to nothing instead.

🎯 Your Turn: match exactly one character

Fill in the blank marked _ using the # 👉 hint so only the single-digit text files match (leaving out file10.txt ), then run it and check the Output panel matches.

🎯 Your Turn: disable globbing with quotes

Make echo print the literal pattern *.txt instead of expanding it, by quoting the argument. Fill in the blank, then run it.

Pro Tips

💡 Preview before you act. Run echo PATTERN (or ls PATTERN ) first to see what a glob will match before you put it after rm — globs expand the same way for every command.
💡 Globs are the shell's job, regex is the tool's job. ls *.log uses a glob, but grep '^ERROR' *.log uses a glob for the filenames and a regex for the line content. Don't mix up the symbols.
💡 Let find do its own matching. In find . -name "*.txt" quote the pattern so the shell doesn't expand it first — find needs to walk every directory itself.
💡 Include dotfiles deliberately with shopt -s dotglob , or by writing the leading dot yourself ( .* ). Turn it back off with shopt -u dotglob .

Common Errors (and the fix)

My program received *.txt literally — there were no matching files, so bash passed the pattern through unchanged. Either create matching files or enable shopt -s nullglob so an empty match expands to nothing.
* didn't include my .env file — a bare * skips dotfiles by design. Write .* for the hidden ones, or turn on shopt -s dotglob .
** only matched the current folder — globstar is off by default. Run shopt -s globstar first to make ** recurse.
My regex .*\.txt matched nothing as a glob — you mixed up the two languages. In a glob it's *.txt ; the regex form belongs inside tools like grep , not on the command line as a filename.
rm * deleted more than I expected — the shell expanded * to every non-hidden name before rm ran. Always preview with echo * first, and quote a literal star if you truly mean the character.

📋 Quick Reference

Pattern

Matches

Notes

Any run of characters

Skips dotfiles; stays in one dir

Exactly one character

One ? per character

[abc]

One char: a, b, or c

Explicit set

[a-z]

One char in a range

Locale-dependent

[!0-9]

One char NOT in the set

^ also negates

{a,b,c}

Generated strings a b c

Not a glob; no files needed

{1..10}

Numeric sequence 1..10

Brace expansion

Recurse into subdirs

Needs shopt -s globstar

Your home directory

Expands to $HOME

"*.txt"

The literal text *.txt

Quoting disables globbing

Frequently Asked Questions

Mini-Challenge: put the wildcards together

No blanks this time — just a brief and an outline. Combine * , ? , bracket sets, brace expansion, and ** in the globdemo folder, and check your output against the hints in the comments.

🎉 Lesson Complete!

✅ * matches any run of characters (but skips dotfiles); ? matches exactly one character
✅ Bracket sets [abc] / ranges [a-z] match one character; [!...] or [^...] negates the set
✅ Brace expansion {a,b} and {1..10} generates strings — it's NOT globbing and needs no matching files
✅ ** recurses after shopt -s globstar ; ~ expands to your home ( $HOME )
✅ Globbing matches filenames in the shell while regex matches text in tools; quote a pattern ( "*.txt" ) to disable expansion, and nullglob makes an unmatched glob vanish
✅ Next lesson: Command Substitution and Expansion — capture command output with $(...) and combine it with the expansions you just learned

Practice quiz

In bash, what does the * wildcard match by default?

Any run of characters in a filename, but NOT files that start with a dot
Exactly one character
Only files that start with a dot
Any text including the / between directories

Answer: Any run of characters in a filename, but NOT files that start with a dot. A bare * matches any sequence of characters (including none) in one filename, but dotfiles are skipped unless you write the leading dot yourself or set dotglob.

Which wildcard matches exactly ONE character?

Answer: ?. ? matches any single character. file?.txt matches file1.txt but not file12.txt.

What does the pattern [a-c]*.txt match?

Any .txt file
Files whose name starts with a, b, or c and ends in .txt
Files named literally a-c.txt
Only file named abc.txt

Answer: Files whose name starts with a, b, or c and ends in .txt. [a-c] is a character range that matches one character a, b, or c, so the pattern matches names beginning with a, b, or c that end in .txt.

How do you write a bracket expression that matches any single character EXCEPT a digit?

A ! (or ^) as the first character inside the brackets negates the set, so [!0-9] matches one character that is not a digit.

Which statement about brace expansion like {a,b,c} is TRUE?

It only works if files matching each item exist
It matches exactly one character like ?
It is identical to a regex alternation and reads files
It is NOT globbing; it generates the strings even when no matching file exists

Answer: It is NOT globbing; it generates the strings even when no matching file exists. Brace expansion is pure text generation done before globbing. echo a{1,2,3} prints a1 a2 a3 whether or not those files exist.

What does the numeric brace expansion {1..5} produce?

1 2 3 4 5
Only 1 and 5
An error in bash
The single string 1..5

Answer: 1 2 3 4 5. Numeric sequence brace expansion {1..5} expands to 1 2 3 4 5.

What must you do before the ** globstar will match across directory levels in bash?

Quote the pattern
Enable it with shopt -s globstar
Run set -e first
Nothing, ** always recurses by default

Answer: Enable it with shopt -s globstar. In bash ** behaves like * unless you enable the globstar option with shopt -s globstar, which lets ** match files and directories recursively.

What does the tilde ~ expand to on its own?

The current directory
The root directory /
A single character
Your home directory, the value of HOME

Answer: Your home directory, the value of HOME. Tilde expansion turns a leading ~ into the path stored in HOME, so ~/notes becomes /home/you/notes.

How can you stop the shell from expanding a glob so a program receives the literal pattern *.txt?

Use a capital STAR
It is impossible to disable globbing
Quote or escape it, for example "*.txt" or \*.txt
Put a space after the star

Answer: Quote or escape it, for example "*.txt" or \*.txt. Globbing happens on unquoted words. Quoting ("*.txt") or escaping (\*.txt) passes the literal pattern through unchanged.

By default in bash, what happens when a glob like *.md matches no files?

The command is skipped silently
The pattern is passed through literally as the text *.md
The shell prints an error and stops
It expands to an empty string

Answer: The pattern is passed through literally as the text *.md. By default bash passes the unmatched pattern through literally as text; enabling shopt -s nullglob makes a non-matching glob expand to nothing instead.

Continue this course

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Next: Command Substitution and Expansion