theIp=""
#1
echo $theIp | while read ip; do
ssh -tt root@$ip
exit
done
#2
while read ip; do
ssh root@$ip
exit
done < <(echo $theIp)
#3
while true; do
ssh root@$theIp
exit
done
the above 3 way about connect any host in a while statement, but only the last one succeeded, why do the first two do nothing?
ssh was eating up your loop's input. Probably in this case your ssh session exits when it gets EOF from it. That's the likely reason but some input may also cause it to exit. You have to redirect its input by specifying < /dev/null or use -n:
ssh -n "root@$ip"
ssh "root@$ip" < /dev/null
That may also apply with -tt since somehow it's independent. Just try.
If you're using Bash or similar shell that supports read -u, you can also specify a differ fd for your file.
while read -u 4 ip; do
ssh root@$ip
exit
done 4< <(echo $theIp)
