Directory thumbnails. Avoid memory limits in ImageMagick using subprocesses.

parallel-thumbnails.sh

#!/bin/bash

set -eu -o pipefail

CMD="$(mktemp)"

for DIR in "$@"
do
  echo "set -xe; montage \\" > "$CMD"

  find "$DIR" -type f -name '*g' \
    | while read FILE
    do
      echo "png:<( convert -resize 150x150 '$FILE' png:- ) \\" >> "$CMD"
    done

  echo "$DIR".jpeg >> "$CMD"

  bash "$CMD"
done