flat_directory.sh

#!/bin/bash

if [ "$#" -ne 1 ]; then
    echo "missing directory"
    echo "Usage: ./flat_directory.sh DIR"
    exit -1
fi

DIR=$1

if [ ! -d "$DIR" ]; then
    echo "Directory '${DIR}' not found"
    exit -1
fi

TARGET="${DIR}-flat"
mkdir -p ${TARGET}
find ${DIR} -type f -print0 | while IFS= read -r -d $'\0' orig; do
    dest=${orig//\//_}
    dest=${dest/$DIR\_/$TARGET\/}
    echo "copying '${orig}' to '${dest}'..."
    cp ${orig} ${dest}
done