zgrep

Overview

zgrep runs grep over gzip-compressed files without manual decompression. Useful for rotated logs (*.gz). Variants exist for other compressors (xzgrep, bzgrep, zstdgrep).

Syntax

zgrep [grep-options] pattern [file...]

Examples with Explanations

Search compressed logs

zgrep -H 'error' /var/log/nginx/access.log.*.gz
zgrep -E 'HTTP/1\.[01]" 5[0-9]{2}' access.log.2.gz

Recursive pattern over mixed trees

find /var/log -name '*.gz' -print0 | xargs -0 zgrep -H 'OutOfMemory'

Count matches

zgrep -c 'ERROR' app.log.gz

Notes & Pitfalls

• Performance is worse than grepping already-decompressed data — decompress hot logs if you query them constantly.
  
• Binary matches: use grep flags carefully (-a, -I).
  
• Confirm whether your zgrep shells out to gzip -dc + grep.

Related Commands

• grep / rg
  
• zcat / zless
  
• journalctl — live system logs
  
• xzgrep / zstdgrep

Additional Resources

• man zgrep