checkconnection/checkconnection.sh

#!/bin/sh

#
## Variables
#

# Testsites should return HTTP-Code "204" 
testsite1="https://datenkastl.de/.connectivity-check"
testsite2="http://captiveportal.kuketz.de"

# Testdomains for ping
testdomain1="datenkastl.de"
testdomain2="metager.de"

#Path of curl and ping
curlbin=`type -tp curl`
pingbin=`type -tp ping`

# Command in case of connection fail.
failcommand="echo Exit without action"

#
## Functions
#

# Check connetction with curl
testwithcurl() {
	echo "Testing with curl..."

	status=$(curl --write-out "%{http_code}\n" "$testsite1"  --silent)
	if [[ "$status" = "204" ]]; then
		echo "The connection is up!"
	
	else

		status2=$(curl --write-out "%{http_code}\n" "$testsite2"  --silent)
		if [[ "$status2" = "204" ]]; then		
			echo "The network is up, but $testsite1 is down."
	
		else
			echo "The network is down."
			$failcommand

		fi
	fi
}

#Check connection with ping
testwithping() {
	echo "Testing with ping..."
	if ping -q -c 1 -W 1 $testdomain1 >/dev/null; then
		echo "The connection is up."
	
	elif ping -q -c 1 -W 1 $testdomain2 >/dev/null; then
		echo "The network is up, but $testdomain1 is down."

	else
		echo "The network is down."
		$failcommand

	fi
}

#
## Main
#

# Set $curlbin and $pingbin to "0" when not installed (workaround for sh)
if [[ ! $curlbin ]]; then curlbin=0; fi
if [[ ! $pingbin ]]; then pingbin=0; fi

# Check network
if [[ -x ${curlbin} ]]; then
	testwithcurl

elif [[ -x ${pingbin} ]]; then
	testwithping

else
	echo "Can't find curl or ping. Please install one of them."
	exit 1
fi