Bash: Breaking out of IF loop in FOR loop - arrays

Question

I am trying to combine a FOR loop (that iterates over IP addresses) and an IF loop (that uses nc to check for a successful ssh connection before moving on).
I have an array ${INSTANCE_IPS[#]} with the IP addresses in it (at the moment it contains 2 IP Addresses). Here is the code:
while [ $ITERATION -le 30 ]
do
for instance in ${INSTANCE_IPS[#]}
do
nc -w 2 $instance 22 > /dev/null
if [ $? -eq 0 ]
then echo "connection succeeded to $instance"
else
ITERATION=$((ITERATION+1))
echo ITERATION=$ITERATION
echo "[info] connection to $instance unsuccessful. trying again. iteration=$ITERATION"
sleep 20
fi
done
done
The 'else' statement in the IF loop works fine. It is the 'then' statement I am having problems with... I don't know how to break out of the IF loop once the connections are successful. Here's an example output when I run the above:
connection succeeded to 10.11.143.171
connection succeeded to 10.11.143.170
connection succeeded to 10.11.143.171
connection succeeded to 10.11.143.170
connection succeeded to 10.11.143.171
connection succeeded to 10.11.143.170
If I use break after then echo "connection succeeded to $instance then it only iterates through 1 IP address and never breaks out:
connection succeeded to 10.11.143.171
connection succeeded to 10.11.143.171
connection succeeded to 10.11.143.171
Ideally I think the best thing to do would be to query the number of elements in the array, then perform a netcat connection an increment some value by 1 until it equals the number of elements in the array, but I'm really not sure how to dot that.
Any help is appreciated :) Please let me know if you need any more information.
Cheers

Answer 1

Reformulate your logic. You can't break if something succeeds, because you don't know whether another item might fail.
Instead, keep a flag saying whether you've successfully gone through all of them, and set it to false if something fails. At this point, you can also break and wait.
ITERATION=0
all_succeeded=false
while [ "$all_succeeded" = "false" -a $ITERATION -le 30 ]
do
all_succeeded=true
for instance in ${INSTANCE_IPS[#]}
do
nc -w 2 $instance 22 > /dev/null
if [ $? -eq 0 ]
then
echo "connection succeeded to $instance"
else
all_succeeded=false
echo "[info] connection to $instance unsuccessful."
sleep 20
break
fi
done
let ITERATION++
done
if [ "$all_succeeded" = "true" ]
then
echo "It worked"
else
echo "Giving up"
fi