Simple PSQL connection tester in bash

test_psql.sh

#!/bin/bash

# ARGV[1]: hostname or IP address to test for postgresql connectivity.
HOST="${1:?A hostname must be passed to this script}"

cleanup() {
  printf '%s\n' "Closing TCP connection to ${HOST}."
  exec 3<&-
  exit
}
trap cleanup EXIT INT

printf '%s\n' "Opening TCP connection to ${HOST}:5432"
exec 3<>/dev/tcp/$HOST/5432

printf '%s\n' 'Sending Postgres client hello message'
printf '\0\0\0\x2f\0\x03\0\0user\0pe-puppetdb\0database\0pe-puppetdb\0\0' >&3

printf '%s\n' 'Postgres response:'
cat <&3
printf '\n'