I’m writing a script to automate some tasks, one of the steps is to wait for a process started on a remote machine to finish execution.

My idea is to show a spinner while the process keeps executing, with inspiration from this question.

The relevant part of the code is this –

spinner_wait_remote() {

    local pid=$1
    local msg=${2-Process $pid still running}
    local spin='-|/'
    local i=0
    while ssh "$remote_machine" "kill -0 $pid" 2>/dev/null
    do
        local i=$(( (i+1) %4 ))
        printf "r${spin:$i:1} $msg"
        sleep .1
    done
    printf "ne[Ae[K"
}

The problem is, it never enters the while loop, although the $pid exists in the remote machine.
I have a similar method that waits for commands launched in the local machine and it works fine. The only difference is the ssh command in the while condition.

I also tried running the entire while loop on the remote machine, but it still doesn’t seem to enter the while loop.

spinner_wait_remote() {

    pid=$1
    msg=${2-Process $pid still running}
    ssh "$remote_server" "
        spin='-|/'
        i=0
        while kill -0 $pid 2>/dev/null
        do
            i=$(( (i+1) %4 ))
            printf "r${spin:$i:1} $msg"
            sleep .1
        done
        printf "ne[Ae[K"
    "
}