add default & remove bash

Dockerfile

@@ -1,4 +1,3 @@
 FROM alpine:3.5
-RUN apk add --no-cache bash
 COPY ping /
-CMD ["/ping"]
+CMD ["sh", "ping"]

README.md

@@ -1,18 +1,15 @@
 # docker-ping
 
 ## ENV
-- `HOSTNAME` Server you would like to continuously ping
+- `HOSTNAME` Server you would like to continuously ping [ default=localhost ]
-- `TIMEOUT` Number of seconds between timeouts
+- `TIMEOUT` Number of seconds between timeouts [ default=300 ]
 
 ## docker-compose.yml
 ```yml
-version: "2"
+...
-
 services:
-
   ping:
     image: willfarrell/ping
-    restart: always
     environment:
       HOSTNAME: "10.0.0.61"
       TIMEOUT: 300

ping

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
-echo ping $HOSTNAME every $TIMEOUT sec
+echo ping ${HOSTNAME:=localhost} every ${TIMEOUT:=300} sec
 
-while true; do ping -c 1 $HOSTNAME; sleep $TIMEOUT; done;
+while true; do ping -c 1 ${HOSTNAME}; sleep ${TIMEOUT}; done;