Using Zsh Glob Qualifiers to Filter Files by Size and Time

Problem: selecting files without external tools

You often need to pick the newest log file, the largest image, or all files modified today. In many shells you would reach for find, sort, and head pipelines, which can be cumbersome for interactive work.

Thesis: zsh glob qualifiers let you filter by attributes directly in the pattern

Glob qualifiers are a zsh‑specific extension that attaches conditions to a filename pattern inside parentheses. They are evaluated by the shell’s glob engine, so the result is produced without spawning external processes.

Syntax basics

A qualifier list appears after the pattern, enclosed in parentheses. Multiple qualifiers can be combined, order does not matter.

pattern(.qualifier1 qualifier2 ...)

For the qualifiers to be recognised, the option extended_glob must be set (it is on by default in many interactive configurations).

Common qualifiers

• . – regular file
• / – directory
• @ – symbolic link
• - – size in bytes (prefix with + for larger, - for smaller)
• m – modification time in days (similar prefix syntax)
• O – order by modification time newest first (O1 gives the newest match)
• o – order by modification time oldest first
• n – numeric sort (useful with versioned filenames)
• N – null‑glob: return empty list instead of error when nothing matches

Worked example: find the five newest PNG images in a tree

Assume you have a directory ~/photos with subfolders and many .png files.

# Enable the option if not already active
setopt extended_glob
# List the five newest PNG files
print -l **/*.png(.nO5)

Explanation:

• **/*.png matches any .png file anywhere under the current directory.
• (.nO5) adds three qualifiers:
• . restricts to regular files (excludes directories named .png).
• n sorts numerically, ensuring img10.png comes after img2.png.
• O5 orders newest first and limits the result to the first five entries.

You can verify the ordering by checking timestamps:

stat -c '%Y %n' **/*.png(.nO5) | sort -nr

Trade‑offs and limitations

Performance: The shell evaluates qualifiers for every candidate match. On a filesystem with millions of files, a broad pattern like **/* can become noticeable; limit the scope with directory prefixes when possible.
Units: The size qualifier - uses bytes, not the 512‑byte blocks used by some find implementations. Double‑check if you are converting from a find command.
Null‑glob behaviour: If no file matches and null_glob is unset, zsh prints an error like "zsh: no matches found". Setting setopt null_glob makes the expression expand to an empty list, which is safer in scripts.
Portability: Glob qualifiers are zsh‑only; scripts that rely on them will not run in bash or dash without modification.

Getting started

Open a zsh session.
Ensure extended globbing is active: setopt extended_glob (add to ~/.zshrc for permanence).
Create a small test set to experiment:
mkdir -p /tmp/zsh-test
cd /tmp/zsh-test
for i in {1..5}; do
    touch -t 2024010${i}0000 file$i.txt
    dd if=/dev/zero of=big$i.bin bs=$((i*100)) count=1 2>/dev/null
 done

Try a few qualifiers and compare with find:
# Newest .txt file
echo *.txt(.Om1)
# Files larger than 250 bytes
echo *.(.s+250)
# All regular files, sorted by size descending
echo *(.OL)

Check results manually if you wish (e.g., ls -l or stat) to confirm the shell’s output matches expectations.