google drive downloader with wget and pure shell script

gdrive-downloader.sh

#!/bin/bash

# acknowledgement:
# https://chemicloud.com/blog/download-google-drive-files-using-wget/#how-to-download-google-drive-files-using-wget
# https://stackoverflow.com/a/6174447

function parse-url() {
    # extract the protocol
    proto="$(echo $1 | grep :// | sed -e's,^\(.*://\).*,\1,g')"
    # remove the protocol
    url="$(echo ${1/$proto/})"
    # extract the path (if any)
    file_id="$(echo $url | grep / | cut -d/ -f4)"
    echo $file_id
}

FILENAME=$2
if [[ -z $FILENAME ]]; then
    echo "File name is not set. Use 'google_file' as name"
    FILENAME='google_file'
fi

FILEID=$(parse-url $1)
CONFIRM=$(wget --quiet --save-cookies /tmp/cookies.txt --keep-session-cookies --no-check-certificate "https://docs.google.com/uc?export=download&id=$FILEID" -O- | sed -rn 's/.*confirm=([0-9A-Za-z_]+).*/\1\n/p')

wget --load-cookies /tmp/cookies.txt \
    "https://docs.google.com/uc?export=download&confirm=$CONFIRM&id=$FILEID" \
    -O $FILENAME && rm -rf /tmp/cookies.txt