rename-seq.bash

#!/usr/bin/env bash
# Usage: {script} DIRECTORY [ PREFIX ]
#
#   --help, h   Displays this help
#
# Report bugs to Henrique Moody <[email protected]>
#

_help()
{
    sed -E 's/^#\s?(.*)/\1/g' "${0}" |
        sed -nE '/^Usage/,/^Report/p' |
        sed "s/{script}/$(basename "${0}")/g"    
}

if [ ${#} -eq 0 ]; then
    _help 1>&2
    exit 1
elif [[ "${1}" == '--help' ]] || [[ "${1}" == '-h' ]]; then
    _help
    exit
fi

DIRECTORY="${1}"
if [ ! -d "${DIRECTORY}" ]; then
    echo "$(basename "${0}"): \`${DIRECTORY}\` is not a valid directory." 1>&2
    exit 2
else
    cd "${DIRECTORY}"
fi

INDEX=1
if [ "${2}" ]; then
    PREFIX="${2}"
else
    PREFIX=$(basename "${PWD}")
fi

COUNT="$(ls -1 | wc -l | awk '{print $1}' | wc -c | awk '{print $1}')"

ls -1rt | while read old_name; do

    number=$(printf "%0${COUNT}d" ${INDEX})
    extension=$(echo "${old_name}" | sed -E 's/.+\.(.+)/\1/g' | tr '[A-Z]' '[a-z]')
    new_name="${PREFIX}-${number}.${extension}"

    if [ -f "${new_name}" ]; then
        echo "File ${new_name} already exists" 1>&2
        exit 3
    fi
    mv -v "${old_name}" "${new_name}"

    let INDEX=${INDEX}+1

done