Bash follow multi process returns

Question

I have a bash script which launch multi process :

while read p || [[ -n $p ]]; do
    hostname=$(echo $p | cut -d';' -f1)
    # On lance les actions en background/parallele
    ssh "$hostname" "someAction.sh" > "$hostname.status.tmp" &
done < hostnames.prm 

The "someAction" script take some times on each server to launch. It returns steps progressively to tell what is going on.

I want to display progressively the state of each action on each process, refreshing the screen.

Example :

Hostname n°1 : 
Step 1 of someAction
Step 2 of someAction
...
Hostname n°2 : 
Step 1 of someAction
Step 2 of someAction
Step 3 of someAction
Step 4 of someAction
someAction finished
...
Hostname n°3 : 
Step 1 of someAction
...
Hostname n°4 : 
Step 1 of someAction
Step 2 of someAction
...
Hostname n°5 : 
Step 1 of someAction
Step 2 of someAction
Step 3 of someAction
Step 4 of someAction
someAction finished

So I store the progress steps return in one file by hostname with :

ssh "$hostname" "someAction..." > "$hostname.status.tmp" &

But then, how can I display them, while at least one process is in progress ?

It seems pretty much hard :/

Answer 1

Thank you for your answer.

I just use :

    clear (go on top of screen)
    ...
    processing=1
actionPids=()

i=0
while read p || [[ -n $p ]]; do
    hostname=$(echo $p | cut -d';' -f1)
    type=$(echo $p | cut -d';' -f2)
    if [[ "$type" = "$ENVIR" || "$ENVIR" = "ALL" || "$hostname" = "$ENVIR" ]]
    then
        # On lance les actions en background/parallele
        doInstance "$hostname" "$ACTION" > "$hostname.status.tmp" &
        actionPids[$i]=$!
    fi
    i=`expr $i + 1`
done < hostnames.prm

lastNbLines=0

tput sc

while [ $processing -eq 1 ]; do
        lastNbLinesTmp=$(cat *.status.tmp | wc -l)
        if [ $lastNbLinesTmp != $lastNbLines ]; then
                tput rc
                tput ed
                echo "======================================================================================="
        fi
        while read p || [[ -n $p ]]; do
                hostname=$(echo $p | cut -d';' -f1)
                type=$(echo $p | cut -d';' -f2)
                if [[ "$type" = "$ENVIR" || "$ENVIR" = "ALL" || "$hostname" = "$ENVIR" ]]
then
                        if [ $lastNbLinesTmp != $lastNbLines ]; then
                                echo -e "${cBold}Server $hostname :${cNone}"
                                cat "$hostname.status.tmp"
                        fi
                fi
        done < $OAAPATH/hostnames.prm
        processing=0
        for actionPid in "${actionPids[@]}"
        do
        if kill -0 $actionPid 2>/dev/null ; then
                processing=1
        fi
        done
        **sleep 1**
        lastNbLines=$lastNbLinesTmp
done

# Wait for all process to finish before exit
wait
rm *.status.tmp

[ $RET_SUM -ne 0 ] && exit 1
exit 0

it works perfectly.

It's a bit complicated, but I think there is no real simplest solution.