RPC is node fully synced

Question

In my test environment, which is ssh,bash and screen, I'm launching a monerod followed by several other programs wallet-rpc/cli and more, which are all depending on monerod.

To prevent any confusion, I would like to wait for monerod to be fully synced, before launching the dependent programs.

Can I RPC the daemon, and get the local blockheight / network blockheight, so I can wait for the sync to complete?

My solution (Updated to wait if daemon is not ready)

get_info() {
    local JSON=$( curl -s -X POST http://127.0.0.1:28081/json_rpc -d '{"jsonrpc":"2.0","id":"0","method":"get_info"}' -H 'Content-Type: application/json' | grep "$1" | grep -o '[0-9]*' )
    [ "${JSON}" = "" ] \
    || {
        echo ${JSON}
        return 0
    } \
    && {
        return 1
    }
}

wait_for_sync() {
    local TARGET=0
    local HEIGHT=0
    local CNT=0
    until [[ ${TARGET} -ne 0 ]]
    do
        ((CNT++))
        echo -en "${WHITE}Waiting for daemon: ${RED}${CNT}${RESTORE}\r"
        sleep 1
        TARGET=$(get_info '"target_height"' | grep -o '[0-9]*')
    done
    echo -ne "\033[2K"
    echo -n "${WHITE}Waiting for daemon to sync: ${HEIGHT}/${TARGET}${RESTORE}"
    while [ ${HEIGHT} -lt ${TARGET} ]
    do
        HEIGHT=$(get_info '"height"' | grep -o '[0-9]*')
        echo -ne "\r${WHITE}Waiting for daemon to sync: ${HEIGHT}/${TARGET}${RESTORE}"
        sleep 1
    done
    echo " ${GREEN}OK Synced${RESTORE}"
}

Answer 1

I have found the best way to deal with this is just to start them all up at once. Monero RPC methods that are dependent on a fully synchronized blockchain will return with a relevant status code if the chain is not fully synced, and thus code can deal with this scenario as and when this happens.

If you find a situation it's imperative the blockchain is fully synchronized before starting some other tool/service, you could call the daemon RPC method get_info which shows you the daemon's current height in the height field and the blockchain target height in the target_height field. Therefore, you are syncing whilst height is less than target_height.