How do I handle hang from an ssh command from my bash script?

Question

I am working on a distributed Linux system.In my bash script I want to grep the output of :

ssh $ipaddress ibstat

The above command will hang if the machine is down. How do I handle the hang and come out of a the bash script with a non-zero value?

Answer 1

Use the ConnectTimeOut option with a low value, which you may need to adjust for your particular environment:

$ ssh -o ConnectTimeout=2 $ipaddress
ssh: connect to host 192.168.123.123 port 22: Connection timed out
$ echo $?
255

You even get a return value which you can test - 255 means an error occurred processing the command.

Answer 2

The timeout utility may be your choice for that:

timeout 5 ssh $ipaddress ibstat

will exit with non-zero result after 5 seconds, set it to a reasonable value sufficient for ibstat to complete

Answer 3

You can try to check host availability first:

if ping -c 1 $ipaddress &> /dev/null
then
  ssh $ipaddress ibstat
else
  exit 1
fi