Checking host availability by using ping in bash scripts
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?
Solution 1:
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
Solution 2:
You don't need the backticks in the if statement. You can use this check
if ping -c 1 some_ip_here &> /dev/null
then
echo 1
else
echo 0
fi
The if command checks the exit code of the following command (the ping). If the exit code is zero (which means that the command exited successfully) the then block will be executed. If it return a non-zero exit code, then the else block will be executed.
Solution 3:
I can think of a one liner like this to run
ping -c 1 127.0.0.1 &> /dev/null && echo success || echo fail
Replace 127.0.0.1 with IP or hostname, replace echo commands with what needs to be done in either case.
Code above will succeed, maybe try with an IP or hostname you know that is not accessible.
Like this:
ping -c 1 google.com &> /dev/null && echo success || echo fail
and this
ping -c 1 lolcatz.ninja &> /dev/null && echo success || echo fail
Solution 4:
There is advanced version of ping - "fping", which gives possibility to define the timeout in milliseconds.
#!/bin/bash
IP='192.168.1.1'
fping -c1 -t300 $IP 2>/dev/null 1>/dev/null
if [ "$?" = 0 ]
then
echo "Host found"
else
echo "Host not found"
fi