CODEWITHSUNDEEP
linuxbash
jmcgrath207
jmcgrath207

Reputation: 2087

How to use ping return value to trigger a bash command

I am trying to make my openvpn client restart if it is not able to ping the destination 4.2.2.2 every 60 seconds, if it is then do nothing. Here is what I have. I want to to be continuously running also.I am running this on Alpine Linux. Any help is greatly appreciated.

#!/bin/sh
#This is a script to continuously do 5 pings to 4.2.2.2
#every 60 seconds to keep the tunnel up if  pings fail,
#then it will restart the openvpn process. And record the
#time it failed.

PING=ping -w 5 4.2.2.2


exec &> /var/log/ping_SLA
while true
do
if 
#ping returns a fail value

    [ $PING -eq 0 ];
        sleep 60s
then
#Execute commands

    date > /var/log/ping_SLA_Fail
        rc-service openvpn stop
        killall -9 openvpn
        rc-service openvpn start
        sleep 30s
else
# colon is a null and is required
    :

fi

done

Upvotes: 2

Views: 14963

Answers (3)

edoloughlin
edoloughlin

Reputation: 5891

You have to run the ping command and then test its exit value:

ping -w 5 4.2.2.2 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    echo "Ping worked"
else
    echo "Ping failed"
fi

Upvotes: 2

MLSC
MLSC

Reputation: 5972

man ping:

-c count

Stop after sending count ECHO_REQUEST packets. With deadline option, ping waits for count ECHO_REPLY packets, until the timeout expires.

-s packetsize

Specifies the number of data bytes to be sent. The default is 56, which translates into 64 ICMP data bytes when combined with the 8 bytes of ICMP header data.

-w deadline

Specify a timeout, in seconds, before ping exits regardless of how many packets have been sent or received. In this case ping does not stop after count packet are sent, it waits either for deadline expire or until count probes are answered or for some error notification from network.

-W timeout

Time to wait for a response, in seconds. The option affects only timeout in absense of any responses, otherwise ping waits for two RTTs.

So we have:

ping -c 1 -s 1 -W 1 4.2.2.2 1>/dev/null 2>&1  #The fast way to ping
#OR : nmap -sP 1 4.2.2.2 1  1>/dev/null 2>&1  #The fastest way to ping
if [ $? -eq 0 ]; then
   date >> /var/log/ping_SLA_Fail
   rc-service openvpn stop
   killall -9 openvpn
   rc-service openvpn start
   sleep 30
elif [ $? -ne 0 ]; then
   .
   .
   .
fi

Upvotes: 3

John B
John B

Reputation: 3646

I'm not familiar with any -w option with ping.

Use the -c option with your ping command to determine the number of ICMP echo requests to send.

Something like this should work: 

if ! ping -c 5 4.2.2.2 &> /dev/null; then
    date >> /var/log/ping_SLA_Fail
    rc-service openvpn stop
    killall -9 openvpn
    rc-service openvpn start
fi
sleep 60

Upvotes: 4

Related Questions