ZSH script to unlock all PDF files in the current directory using a single password

pdfunlock.zsh

#!/usr/bin/env zsh
set -u
setopt extendedglob nullglob

SCRIPT_NAME=${0:t}

usage() {
  cat <<EOF
Usage: $SCRIPT_NAME [options] [input_dir]

Unlock all PDF files in input_dir (or current directory if omitted).
Unlocked files are written to: input_dir/unlocked/

Options:
  -i, --input DIR   Input directory (optional; can also be given positionally)
  -h, --help        Show this help message and exit

Requirements:
  - zsh
  - qpdf

Notes:
  - Matching is case-insensitive (*.pdf, *.PDF, ...)
  - Only regular files are processed
  - Already-unlocked PDFs are skipped
  - Existing output files are not overwritten
EOF
}

# --- Parse args ---
indir="."
while (( $# > 0 )); do
  case "$1" in
    -h|--help)
      usage
      exit 0
      ;;
    -i|--input)
      shift
      if [[ -z "${1:-}" ]]; then
        echo "Error: --input requires a directory path."
        exit 1
      fi
      indir="$1"
      shift
      ;;
    --) # end of options
      shift
      break
      ;;
    -*)
      echo "Unknown option: $1"
      echo
      usage
      exit 1
      ;;
    *)
      # positional input dir (only one supported)
      indir="$1"
      shift
      ;;
  esac
done

# --- Validate input directory ---
if [[ ! -d "$indir" ]]; then
  echo "Error: input directory not found: $indir"
  exit 1
fi

# --- Dependency check ---
if ! command -v qpdf >/dev/null 2>&1; then
  echo "Error: qpdf is not installed or not in PATH."
  echo "Install it with:"
  echo "  macOS (brew): brew install qpdf"
  echo "  Debian/Ubuntu: sudo apt install qpdf"
  exit 1
fi

# --- Output directory is unlocked subdir of input dir ---
outdir="$indir/unlocked"
mkdir -p -- "$outdir"

# --- Collect PDFs from input dir (case-insensitive, regular files only) ---
pdfs=( "$indir"/*.(#i)pdf(.N) )
if (( ${#pdfs} == 0 )); then
  echo "No PDF file found in: $indir"
  exit 0
fi

echo "Input directory: $indir"
echo "Output directory: $outdir"
echo "Found ${#pdfs} PDF file(s):"
for f in "${pdfs[@]}"; do
  print -- "  ${f:t}"
done
echo

# --- Prompt for password ---
read -rs "PW?Password: "
echo

skipped=0
unlocked=0
failed=0

# --- Process each PDF ---
for f in "${pdfs[@]}"; do
  out="$outdir/${f:t:r}_unlocked.pdf"

  encinfo="$(qpdf --show-encryption "$f" 2>/dev/null || true)"
  if [[ "$encinfo" == *"File is not encrypted"* ]]; then
    echo "Skipping (already unlocked): ${f:t}"
    ((skipped++))
    continue
  fi

  if [[ -f "$out" ]]; then
    echo "Skipping (output already exists): ${f:t} -> ${out:t}"
    ((skipped++))
    continue
  fi

  echo "Unlocking: ${f:t} -> ${out:t}"
  if qpdf --password="$PW" --decrypt "$f" "$out" 2>/dev/null; then
    ((unlocked++))
  else
    echo "Failed to unlock: ${f:t}"
    rm -f -- "$out" 2>/dev/null || true
    ((failed++))
  fi
done

echo
echo "Outcome:"
echo "  Unlocked: $unlocked"
echo "  Skipped : $skipped"
echo "  Failed  : $failed"