File: wait-for

#!/bin/sh

TIMEOUT=15
QUIET=0

echoerr() {
  if [ "$QUIET" -ne 1 ]; then printf "%s\n" "$*" 1>&2; fi
}

usage() {
  exitcode="$1"
  cat <<USAGE >&2
Usage:
  command host:port [-t timeout] [-- command args]
  -q | --quiet                        Do not output any status messages
  -t TIMEOUT | --timeout=timeout      Timeout in seconds, zero for no timeout
  -- COMMAND ARGS                     Execute command with args after the test finishes
USAGE
  exit "$exitcode"
}

wait_for() {
  if ! command -v nc >/dev/null; then
    echoerr 'nc command is missing!'
    exit 1
  fi

  for i in $(seq $TIMEOUT); do
    nc -z "$HOST" "$PORT" >/dev/null 2>&1

    result=$?
    if [ $result -eq 0 ]; then
      if [ $# -gt 0 ]; then
        exec "$@"
      fi
      exit 0
    fi
    sleep 1
  done
  echo "Operation timed out" >&2
  exit 1
}

while [ $# -gt 0 ]; do
  case "$1" in
  *:*)
    HOST=$(printf "%s\n" "$1" | cut -d : -f 1)
    PORT=$(printf "%s\n" "$1" | cut -d : -f 2)
    shift 1
    ;;
  -q | --quiet)
    QUIET=1
    shift 1
    ;;
  -t)
    TIMEOUT="$2"
    if [ "$TIMEOUT" = "" ]; then break; fi
    shift 2
    ;;
  --timeout=*)
    TIMEOUT="${1#*=}"
    shift 1
    ;;
  --)
    shift
    break
    ;;
  --help)
    usage 0
    ;;
  *)
    echoerr "Unknown argument: $1"
    usage 1
    ;;
  esac
done

if [ "$HOST" = "" ] || [ "$PORT" = "" ]; then
  echoerr "Error: you need to provide a host and port to test."
  usage 2
fi

wait_for "$@"