List sub-domains using crt.sh

crt.sh

#!/bin/bash
# List sub-domains using crt.sh
set -euo pipefail
IFS=$'\n\t'

error() {
  echo "[ERROR] $*"
  exit 1
}

command_exists () {
  command -v "$1" >/dev/null 2&>/dev/null
}

if ! command_exists jq ; then
  error 'jq is not installed'
fi
if ! command_exists curl ; then
  error 'curl is not installed'
fi

DOMAIN=$*
if [ -z $DOMAIN ] ; then
  error 'Usage: ./crt.sh <domain>'
fi

curl -sS "https://crt.sh?q=%.${DOMAIN}&output=json" | jq .name_value | sort -u