How to check if a server is running

Question

I want to use ping to check to see if a server is up. How would I do the following:

ping $URL
if [$? -eq 0]; then
    echo "server live"
else
    echo "server down"
fi

How would I accomplish the above? Also, how would I make it such that it returns 0 upon the first ping response, or returns an error if the first ten pings fail? Or, would there be a better way to accomplish what I am trying to do above?

Answer 1

I'ld recommend not to use only ping. It can check if a server is online in general but you can not check a specific service on that server.

Better use these alternatives:

curl

man curl

You can use curl and check the http_response for a webservice like this

check=$(curl -s -w "%{http_code}\n" -L "${HOST}${PORT}/" -o /dev/null)
if [[ $check == 200 || $check == 403 ]]
then
    # Service is online
    echo "Service is online"
    exit 0
else
    # Service is offline or not working correctly
    echo "Service is offline or not working correctly"
    exit 1
fi

where

• HOST = [ip or dns-name of your host]

• (optional )PORT = [optional a port; don't forget to start with :]

• 200 is the normal success http_response

• 403 is a redirect e.g. maybe to a login page so also accetable and most probably means the service runs correctly

• -s Silent or quiet mode.

• -L Defines the Location

• -w In which format you want to display the response
  -> %{http_code}\n we only want the http_code

• -o the output file
  -> /dev/null redirect any output to /dev/null so it isn't written to stdout or the check variable. Usually you would get the complete html source code before the http_response so you have to silence this, too.

---

nc

man nc

While curl to me seems the best option for Webservices since it is really checking if the service's webpage works correctly,

nc can be used to rapidly check only if a specific port on the target is reachable (and assume this also applies to the service).

Advantage here is the settable timeout of e.g. 1 second while curl might take a bit longer to fail, and of course you can check also services which are not a webpage like port 22 for SSH.

nc -4 -d -z -w 1 &{HOST} ${PORT} &> /dev/null
if [[ $? == 0 ]]
then
    # Port is reached
    echo "Service is online!"
    exit 0
else
    # Port is unreachable
    echo "Service is offline!"
    exit 1
fi

where

• HOST = [ip or dns-name of your host]

• PORT = [NOT optional the port]

• -4 force IPv4 (or -6 for IPv6)

• -d Do not attempt to read from stdin

• -z Only listen, don't send data

• -w timeout
  If a connection and stdin are idle for more than timeout seconds, then the connection is silently closed. (In this case nc will exit 1 -> failure.)

• (optional) -n If you only use an IP: Do not do any DNS or service lookups on any specified addresses, hostnames or ports.

• &> /dev/null Don't print out any output of the command

Answer 2

You can use something like this -

serverResponse=`wget --server-response --max-redirect=0 ${URL} 2>&1`

if [[ $serverResponse == *"Connection refused"* ]]
then
    echo "Unable to reach given URL"
    exit 1
fi

Answer 3

Use the -c option with ping, it'll ping the URL only given number of times or until timeout

if ping -c 10 $URL; then
    echo "server live"
else
    echo "server down"
fi