Command line and power tools

What the shell does to your asterisk

Updated 2026-08-08 · 4 min read

The difference between rm *.log doing what you meant and doing something memorable is understanding one fact: the shell, not the command, expands the pattern — before the command ever runs.

The expansion, made visible

When you type ls *.pdf, zsh replaces *.pdf with the actual matching filenames and *then* runs ls. Seeing the expansion is one keystroke away — type the pattern and press Tab, or preview safely:

echo *.pdf

echo is the dry run for any glob: it prints exactly what the destructive command would receive.

The patterns

Pattern	Matches
*.pdf	any .pdf in this folder
report-?.pdf	one single character
*.[jp]*g	.jpg, .jpeg, .png-ish sets
**/*.pdf	recursive, all subfolders

is the one worth installing into your fingers: ls /*.sketch finds every Sketch file below here, no find command required. It works in default macOS zsh; bash needs shopt -s globstar.

The three traps

Hidden files are excluded. * skips dotfiles by design — cp * /backup silently leaves .env behind. Match them deliberately with .* or zsh's *(D).

No match is an error in zsh. A pattern matching nothing aborts the command (zsh: no matches found) — safer than bash, which passes the literal *.pdf to the program as text, producing the classic confusing failure inside the command instead.

Spaces are fine, quoting is not. A *quoted* glob is literal: rm "*.log" tries to delete one file named asterisk-dot-log. Quote filenames, never patterns.

Globs or find?

Globs are for the current situation — quick, visual, interactive. The find command is for conditions globs cannot express (size, age, type) and for scripts, where its explicitness is a feature. The practical split: glob until the question involves *when* or *how big*, then reach for find.

Common questions

Why does my glob say 'no matches found'?

zsh treats a non-matching pattern as an error rather than passing it through. The pattern is wrong for this folder — echo it to see, or check hidden-file and case issues.

How do I match files in all subfolders?

The pattern: /*.pdf expands recursively in zsh. It replaces a whole class of simple find invocations.