How to get sha256 fingerprints for use with Jenkins Swarm client's -sslFingerprints option

get_sslFingerprints.sh

#!/bin/bash

sslFingerprint=$(echo \
  | openssl s_client -showcerts -connect $some_jenkins_server_fqdn_name:443 2> /dev/null \
  | openssl x509 -noout -sha256 -fingerprint | awk -F'=' '{print $NF}')

# Note that you can strip the colons for a shorter fingerprint:
echo $sslFingerprint | tr -d ':'

# But you do not need to strip them.
#  (SwarmClient.DefaultTrustManager will do it for you:
#   https://github.com/jenkinsci/swarm-plugin/blob/master/client/src/main/java/hudson/plugins/swarm/SwarmClient.java ,
#   esp. "StringUtils.remove(fingerprint.toLowerCase(), ':')"
#   on line 723, https://github.com/jenkinsci/swarm-plugin/blob/44568f3e23b1d3433a0ab86078b2cc8160e906ff/client/src/main/java/hudson/plugins/swarm/SwarmClient.java#L723)

# See Jenkins's Swarm Plugin for more:
# * https://wiki.jenkins.io/display/JENKINS/Swarm+Plugin
# * https://github.com/jenkinsci/swarm-plugin

#