Gzip Old Log Files Shell Script

Logrotate handles many apps, but custom app folders still need a gzip old log files shell script — find by age, compress, and optionally prune archives before disks fill.

What this script does

Targets directory argument (default /var/log/myapp)
Compresses *.log older than N days
Skips *.gz files
Optional DELETE_DAYS removes ancient .gz
Dry-run mode lists actions

Prerequisites

find and gzip
Write permission on log dir
Test dry-run before production cron

Step 1: Save the script

sudo nano /usr/local/bin/gzip-old-logs.sh
sudo chmod +x /usr/local/bin/gzip-old-logs.sh

Step 2: Full script (scroll to read)

gzip-old-logs.sh

#!/usr/bin/env bash
set -euo pipefail

DIR="${1:-/var/log/myapp}"
AGE_DAYS="${2:-7}"
DELETE_DAYS="${DELETE_DAYS:-90}"
DRY="${DRY_RUN:-0}"
LOG="/var/log/gzip-old-logs.log"

log(){ echo "[$(date '+%F %T')] $*" | tee -a "$LOG"; }

[[ -d "$DIR" ]] || { log "missing dir $DIR"; exit 1; }

do_gzip(){
  local f="$1"
  if (( DRY )); then
    log "DRY gzip $f"
  else
  gzip -f "$f" && log "gzipped $f"
  fi
}

while IFS= read -r -d '' f; do
  do_gzip "$f"
done < <(find "$DIR" -type f -name '*.log' -mtime +"$AGE_DAYS" -print0 2>/dev/null)

while IFS= read -r -d '' f; do
  if (( DRY )); then
    log "DRY delete $f"
  else
    rm -f "$f" && log "deleted $f"
  fi
done < <(find "$DIR" -type f -name '*.gz' -mtime +"$DELETE_DAYS" -print0 2>/dev/null)

Scroll inside the box to read the full script.

Step 3: Configure settings

Works alongside custom log rotation
Alert before cleanup: disk space alert
Do not gzip logs still open by a running process without copytruncate policy

Step 4: Test manually

DRY_RUN=1 ./gzip-old-logs.sh /var/log/nginx

sudo ./gzip-old-logs.sh /var/log/app 14

Schedule with cron

sudo crontab -e

Add:

15 3 * * * /usr/local/bin/gzip-old-logs.sh /var/log/myapp 7 >> /var/log/gzip-old-logs.log 2>&1

Gzip Old Log Files Shell Script Linux (find, mtime, Cron)