Bash Script to Clean Up Old Files and Alert on High Disk Usage

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

# === CONFIG DEFAULTS ===
TARGET_DIR="${1:-/var/log}"
DAYS_OLD="${2:-14}"
LOG_FILE="${3:-/var/log/homelab_cleanup.log}"
DISK_PATH="${4:-/}"
DISK_THRESHOLD="${5:-85}"
DRY_RUN="${DRY_RUN:-false}"

timestamp() { date +"%Y-%m-%d %H:%M:%S"; }

log() {
  echo "$(timestamp) $*" | tee -a "$LOG_FILE" >/dev/null
}

require_cmd() {
  command -v "$1" >/dev/null 2>&1 || { echo "Missing required command: $1" >&2; exit 1; }
}

main() {
  require_cmd find
  require_cmd df
  require_cmd awk

  if [[ ! -d "$TARGET_DIR" ]]; then
    echo "Target directory does not exist: $TARGET_DIR" >&2
    exit 1
  fi

  log "=== Cleanup start ==="
  log "TARGET_DIR=$TARGET_DIR DAYS_OLD=$DAYS_OLD DISK_PATH=$DISK_PATH THRESHOLD=${DISK_THRESHOLD}% DRY_RUN=$DRY_RUN"

  CANDIDATES_COUNT="$(find "$TARGET_DIR" -type f -mtime "+$DAYS_OLD" 2>/dev/null | wc -l | tr -d ' ')"
  log "Found $CANDIDATES_COUNT files older than $DAYS_OLD days."

  if [[ "$CANDIDATES_COUNT" -gt 0 ]]; then
    if [[ "$DRY_RUN" == "true" ]]; then
      log "DRY RUN: Listing files that would be deleted:"
      find "$TARGET_DIR" -type f -mtime "+$DAYS_OLD" -print | tee -a "$LOG_FILE" >/dev/null
    else
      log "Deleting files..."
      find "$TARGET_DIR" -type f -mtime "+$DAYS_OLD" -print -delete | tee -a "$LOG_FILE" >/dev/null
      log "Deletion complete."
    fi
  fi

  USED_PCT="$(df -P "$DISK_PATH" | awk 'NR==2 {gsub(/%/,"",$5); print $5}')"
  log "Disk usage for $DISK_PATH is ${USED_PCT}%."

  if [[ "$USED_PCT" -ge "$DISK_THRESHOLD" ]]; then
    log "ALERT: Disk usage is high (${USED_PCT}% >= ${DISK_THRESHOLD}%)."
    echo "ALERT: Disk usage high on $DISK_PATH: ${USED_PCT}%"
  fi

  log "=== Cleanup end ==="
}

main "$@"