Sync folder with Google Drive. Recursively downloads with wget and Google Drive public links. Used to sync ebooks to my eReaders (Kobo). Be warned that public links are dangerous as they could allow someone to download your files. Be sure to use this only in secure environments. This has been tested to be used in POSIX shells as well as in bash.

sync.sh

#!/bin/sh

set -x


#input sharelink here. Example: https://drive.google.com/folderview?id=0B1g-MbiD2F6vdtOT92b3MoerO&usp=sharing
# SHARELINK="https://drive.google.com/folderview?id=idU&usp=sharing"
SHARELINK="https://drive.google.com/folderview?id=0B8HjeRxyzNm7RjZIdDFVWHkxeXM&usp=sharing"
DESTINATION="/mnt/onboard/gdrive"
# Change following to false when you don't want to delete files when they are missing from google drive. This can
REMOVEFILES=false

# Begin code

download () {
        url=$1
        folder=$2
        changed=$3

        wgetoutput="`wget --no-check-certificate -qO- $url 2>&1`"
        mkdir -p "$folder"
        commands="$(echo "$wgetoutput" | grep -Eo '\[,,\"(.*?)\",,,,,\"(.*?)\"')"
        missingfiles="$(find "$folder" -type f -print)"
        missingdirectories="$(find "$folder" -type d -print)"

        #Go to next

        subfolders="$(echo "$wgetoutput" | grep -Eo '\[,".*?\",\".*?folder' | cut -c 4- | cut -d\" -f 1)"
        IFS="
"
        for subfolder in $subfolders; do
                name=$(echo "$wgetoutput" | grep -Eo 'entry-'$subfolder'.*?</div></div><div class=\"flip-entry-title\">(.*?)</div>' | grep -Eo 'entry-title">.*?</div>$' | cut -c 14- | sed 's/<\/div>//')
                newdest="$2/$name"
                escapedfile="$(echo "$newdest" | sed -e 's/[]\$*.^|[]/\\&/g')"
                missingdirectories=$(echo "$missingdirectories" | sed -e "s@$escapedfile@@g" | sed '/^$/d')
                output=$(download "https://drive.google.com/folderview?id=$subfolder&usp=sharing" "$newdest" $changed)
                changed=$output
        done

        #Download files
        echo "Downloading for $folder..." 1>&2;
        for line in $commands; do
                id=$(echo "$line" | grep -Eio \"[0-9a-z]+\" | head -1 | tr -d '"')
                name=$(echo "$line" | sed -e 's/\[,,\"//' | sed s/\".*//'')
                file="$folder/$name"
                cmd=$(echo "wget --no-check-certificate -nc -q --no-cookies -O \"$file\" \"https://docs.google.com/uc?export=download&id="$id"\"")
                eval "$cmd"
                commandresult=$?
                if [ "$commandresult" -eq 0 ]; then
                        echo "Downloaded: $file" 1>&2;
                        changed=$(($changed + 1))
                else
                        echo "Skipped (Already exists or error): $file" 1>&2;
                fi
                escapedfile=$(echo "$file" | sed -e 's/[]@$*.^|[]/\\&/g')
                missingfiles=$(echo "$missingfiles" | sed 's@'$escapedfile'@@g' | sed '/^$/d')
        done
        echo "Finished downloading!" 1>&2;

        #Remove missing files
        if [ $REMOVEFILES = true ]; then
                echo "Checking files to remove from $folder..." 1>&2;
                i=0
                for line in $missingfiles; do
                                echo "Removing file: $line" 1>&2;
                                rm -f "$line"
                                changed=$(($changed + 1))
                done
                for line in $missingdirectories; do
                                echo "Removing directory: $line" 1>&2;
                                rm -rf "$line"
                                changed=$(($changed + 1))
                done
                echo "Finished scan!" 1>&2;
        fi

        echo $changed
}

result=$(download "$SHARELINK" "$DESTINATION" 0)
echo "Changed: $result files/folders"
if [ $result -ne 0 ]; then
        echo "Sync made changes to disk!"
fi