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.

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 {' '} and {' '} — Not Globbing!

Brace expansion is not globbing. The shell generates strings from the braces before any filename matching, so echo file{' '}.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.

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.

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

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.

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.