diff --git a/run.sh b/run.sh
index 3a761aa..1d6c929 100755
--- a/run.sh
+++ b/run.sh
@@ -1,24 +1,25 @@
 #!/usr/bin/env bash
 
-set -eu
+set -o errexit -o nounset
 
+# as suggested in https://github.com/koalaman/shellcheck/wiki/SC2044
 shopt -s globstar nullglob
 
 OCRMYPDF_CMD='docker run --rm -i ocrmypdf'
 
-SRC_DIR=./test
-DST_DIR=./dst
+SCR_DIR=/mnt/docscans
+DST_DIR=/mnt/documents
 
+LOCKFILE=$DST_DIR/.lock
+ARCHIVE_DIR=$DST_DIR/archive
 FAILED_DIR=$DST_DIR/failed
 LOG_DIR=$DST_DIR/logs
-ARCHIVE_DIR=$DST_DIR/archive
 
-mkdir -p "$DST_DIR"
-mkdir -p "$ARCHIVE_DIR"
+PROCESSED_COUNT=0
+FAILED_COUNT=0
 
 function ocrFile() {
   SRC=$1
-  DST_DIR=$2
   FILE_NAME=$(basename -- "$SRC")
 
   DST_PDF=$DST_DIR/${FILE_NAME%.*}.pdf
@@ -34,13 +35,31 @@ function ocrFile() {
     > "$DST_PDF" 2> "$DST_LOG"
 }
 
-for FILE in "$SRC_DIR"/*.pdf
-do
-  echo "processing $FILE..."
-  ocrFile "$FILE" "$DST_DIR"
-  # TODO: move to FAILED_DIR and error out
-  echo processed "$FILE"
-  mv "$FILE" "$ARCHIVE_DIR"
-  echo moved "$FILE" to archive
-done
+exec 100>$LOCKFILE || exit 23
+
+flock -n 100 || { echo $LOCKFILE is locked; exit 1; }
+
+mkdir -p "$DST_DIR" "$ARCHIVE_DIR" "$FAILED_DIR" "$LOG_DIR"
+
+while IFS= read -r -d '' file
+do
+  echo "processing $FILE ..."
+
+  if ocrFile "$FILE" "$DST_DIR"
+  then
+    echo processed "$FILE"
+    mv "$FILE" "$ARCHIVE_DIR"
+    echo moved "$FILE" to "$ARCHIVE_DIR"
+    (( PROCESSED_COUNT++ ))
+  else
+    echo failed to process "$FILE"
+    mv "$FILE" "$FAILED_DIR"
+    echo moved "$FILE" to "$FAILED_DIR"
+    (( FAILED_COUNT++ ))
+  fi
+done <   <(find $SCR_DIR -maxdepth 1 -name '*.pdf' -print0)
+
+echo Done
+echo processed $PROCESSED_COUNT PDFs
+[ $FAILED_COUNT -gt 0 ] && echo failed on $FAILED_COUNT PDFs