Question

I’ve been banging my head against for wall for a while with this one.

I want to SSH into a set of machines and check whether they are available (accepting connections and not being used). I have created a small script, tssh, which does just that:

#!/bin/bash  host=$1 timeout=${2:-1}  ssh -qo 'ConnectTimeout $timeout' $host '[ \`who | cut -f1 | wc -l \` -eq 0 ] && exit 0 || exit 1' 

This script works correctly. Returning 255 if there was a connection problem, 1 if the machine is busy and 0 if everything is good. If anyone knows a better way to do this please let me know.

So next I try and call tssh on my set of machines using a while read loop, and this is where it all goes wrong. The loop exits as soon as tssh returns 0 and never completes the full set.

while read nu ; do tssh 'MYBOXES$nu' ; done < <(ruby -e '(0..20).each { |i| puts i }') 

At first I thought this was a subshell problem but apparently not. Any help, along with comments on style/content, would be much appreciated! I know I’m going to kick myself when I find out why…

Answer 1

Don’t know if it would help, but a cleaner way of writing that would be

for nu in `ruby -e '(0..20).each { |i| puts i}'`; do   tssh 'MYBOXES$nu'  done