Group files under the target directory into yyyy-mm date directories.

group-by-date.sh

#!/bin/sh

target_dir=$1

if [ ! "$target_dir" ]; then
    echo "Usage: $0 <target dir>"
    exit 0
fi

if [ ! -d "$target_dir" ]; then
    echo "The target dir $target_dir does not exist."
    exit 0
fi

cd "$target_dir"

file_list=$(find "$PWD" -type f)

IFS=$'\n'
for file in $file_list; do
    if [ "$file" == "$0" ]; then
        continue
    fi
    date=$(stat -f "%Sm" -t "%Y-%m" "$file")
    mkdir -p $date
    cp -pv "$file" $date
    rm "$file"
done