Bash getopts Shell Script | CLI Flags on Linux

Scripts run by humans and by cron benefit from predictable flags. getopts is the portable way to parse -d /path -r 14 without fragile manual $1 $2 shifting.

What this script does

Implements -d directory and -r retention days
Shows -h usage text
Rejects unknown options with a clear error
Example compresses and deletes old *.log files
Safe defaults when flags are omitted

Prerequisites

Bash on Linux
Target log directory exists and is writable
gzip installed for compression step

Step 1: Save the script

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

Step 2: Full script (scroll to read)

rotate-logs.sh

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

DIR="/var/log/myapp"
RETENTION=14

usage(){
  cat <<EOF
usage: $0 [-d logdir] [-r days]
  -d  directory to clean (default: $DIR)
  -r  delete .log files older than N days (default: $RETENTION)
  -h  help
EOF
  exit "${1:-0}"
}

while getopts ":d:r:h" opt; do
  case "$opt" in
    d) DIR="$OPTARG" ;;
    r) RETENTION="$OPTARG" ;;
    h) usage 0 ;;
    :) echo "Option -$OPTARG requires an argument"; usage 1 ;;
    \?) echo "Unknown option: -$OPTARG"; usage 1 ;;
  esac
done

[[ -d "$DIR" ]] || { echo "Not a directory: $DIR"; exit 1; }
[[ "$RETENTION" =~ ^[0-9]+$ ]] || { echo "Retention must be integer"; exit 1; }

echo "Compressing logs older than ${RETENTION} days in $DIR"
find "$DIR" -type f -name '*.log' -mtime +"$RETENTION" -print -exec gzip -9 {} \;
find "$DIR" -type f -name '*.log.gz' -mtime +"$RETENTION" -print -delete
echo "Done"

Scroll inside the box to read the full script.

Step 3: Configure settings

getopts only handles short options; use getopt (GNU) for long options like –dry-run
Complements custom log rotation script

Bash getopts shell script parsing command line flags

Step 4: Test manually

./rotate-logs.sh -h

./rotate-logs.sh -d /var/log/myapp -r 7

Schedule with cron

sudo crontab -e

Add:

0 4 * * * /usr/local/bin/rotate-logs.sh -d /var/log/myapp -r 30

Bash getopts Shell Script: Parse -d -r Flags for Linux CLI Tools