how to handle server being down when piping curl to grep

Question

I am trying to write a script to query a web server API and check for a value but I am having trouble trying to figure out how to best go about it. So far what I am doing is using curl to get a response and then piping that to grep to look for a pattern. If the pattern exist, I do one thing, if not, I do another.

if curl http://192.168.1.2:8080/api/query | grep -q mypattern; then
    echo "success"
    else echo "boo"
fi

But if the server is down I don't know how to handle that neatly because the server being down produces the same result as not finding the pattern. What I want to happen is for curl to keep making the request until the server responds and then grep the result. I know I could probably do it but it will be very kludgy. One thought was a loop to curl first until the exit code is 0 but I'm sure there is a more practical way. Any ideas?

Answer 1

One can use $PIPESTATUS:

#!/bin/bash
if curl http://192.168.1.2/api/query | grep -q mypattern; then
  echo "Found pattern"
elif [ "${PIPESTATUS[0]}" -eq 0 ]; then
  echo "Server up"
else
  echo "Server down"
fi