Checking host availability by using ping in bash scripts

bash networking ping connectivity
burtek picture burtek · Aug 8, 2013 · Viewed 241.7k times · Source

I want to write a script, that would keep checking if any of the devices in network, that should be online all day long, are really online. I tried to use ping, but

if [ "`ping -c 1 some_ip_here`" ]
then
  echo 1
else
  echo 0
fi

gives 1 no matter if I enter valid or invalid ip address. How can I check if a specific address (or better any of devices from list of ip addresses) went offline?

Answer

StianE picture StianE · Aug 8, 2013

Ping returns different exit codes depending on the type of error.

ping 256.256.256.256 ; echo $?
# 68

ping -c 1 127.0.0.1 ; echo $?
# 0

ping -c 1 192.168.1.5 ; echo $?
# 2

0 means host reachable

2 means unreachable

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