How to check internet access using bash script in linux?

Question

In my school, the internet is not available(every night after 23:0 the school will kill the internet, to put us in bed >..<), then the ping will never stop, though I have use

Answer 1

Reliable old ping in a separate bash script:

#!/bin/bash
ipaddr='8.8.8.8' # Google's public DNS server
[[ -z `ping -c1 $ipaddr |& grep -o 'Network is unreachable'` ]] || exit 1
[[ -z `ping -c3 $ipaddr |& grep -o '100% packet loss'` ]] && exit 0 || exit 1

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Put this on a separate script. It will handle different network situations as (1) not being connected to a network, (2) connected to the network but cannot access the internet (or at least Google), and (3) connected to the internet.

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You may later use the exit code of the script to check connectivity, e.g.

~$ script-name && echo online || echo offline