Read line from stdin and run command on it - bash

Question

I'm trying to get the following command to work
gcloud compute instances list --format=json --regexp .*gluster.* | jq '.[].networkInterfaces[].networkIP' | tr -d '\"' | while read i; do gcloud compute ssh --zone $ZONE ubuntu#gluster-1 -- "sudo gluster peer probe $i && cat >> peers.txt"; done
Basically the gcloud command gives:
gcloud compute instances list --format=json --regexp .*gluster.* | jq '.[].networkInterfaces[].networkIP' | tr -d '\"'
10.128.0.2
10.128.0.3
10.128.0.4
However running the above command only gives seems to only run on the first ip which is the host, giving the warning
peer probe: success. Probe on localhost not needed
And none of the other nodes get connected.
Notes:
Weirdly running the gcloud command on the second node connects to the first one, running on the third doesn't do anything at all
The peers.txt file on all the nodes except the the third have again weirdly only the two latter ips
ubuntu#gluster-1:~$ cat peers.txt
10.128.0.3
10.128.0.4
Running echo on the value in the loop gives
gcloud compute instances list --format=json --regexp .*gluster.* | jq '.[].networkInterfaces[].networkIP' | tr -d '\"' | while read i; do echo ip: $i; done
ip: 10.128.0.2
ip: 10.128.0.3
ip: 10.128.0.4

Answer 1

There is nothing wrong with piping into a loop (assuming you don't need the body of the loop to execute in the current shell). You don't want to use a for loop for something like this, though; see Bash FAQ 001 for more information. Use a while loop.
gcloud compute instances list --format=json --regexp .*gluster.* |
jq -r '.[].networkInterfaces[].networkIP' |
while IFS= read -r ipaddr; do
echo "$ipaddr"
done
(Note that using the -r option with jq eliminates the need to pipe the output into tr to remove the double quotes.)
The problem you may be seeing is that the command you put in the while loop also reads from standard input, which consumes data from your pipeline before read can read it. In that case, you can redirect standard input from /dev/null:
gcloud compute instances list --format=json --regexp .*gluster.* |
jq -r '.[].networkInterfaces[].networkIP' |
while IFS= read -r i; do
gcloud compute ssh --zone $ZONE ubuntu#gluster-1 \
-- "sudo gluster peer probe $i < /dev/null &&
cat >> peers.txt"
done
Or, use a process substitution to read from a different file descriptor.
while IFS= read -r i <&3; do
gcloud ...
done 3< <(gcloud compute instances .. | jq -r '...')

Answer 2

Got it to work with a for loop.
Also learnt that for loops aren't for piping into :)
for item in $(gcloud compute instances list --format=json --regexp .*gluster.* | jq '.[].networkInterfaces[].networkIP' | tr -d '\"'); do gcloud compute ssh --zone $ZONE ubuntu#gluster-1 -- "sudo gluster peer probe $item && echo $item >> peers.txt"; done