Check signed SSH cert for expiration

ssh-signed.zshrc

# .zhsrc
function signed {
  expiry=$(ssh-keygen -L -f ~/.ssh/id_rsa-cert.pub | grep Valid | awk '{ print $5 }')
  expiry_epoch=$(date -j -f "%Y-%m-%dT%H:%M:%S" "${expiry}" "+%s")
  current_epoch=$(date "+%s")
  if [ $current_epoch -gt $expiry_epoch ]; then
    echo $fg[red] "SSH -"
    return -1
  else
    (( seconds_left = $expiry_epoch - $current_epoch ))
    (( hours = seconds_left / 60 / 60 ))
    (( minutes = seconds_left / 60 % 60 ))
    (( seconds = seconds_left % 60 ))
    echo $fg[green] "SSH + $hours:${(l(2)(0))minutes}:${(l(2)(0))seconds} remaining"
    return 0
  fi
}