Bash loop ping successful - bash

Question

I'm thinking that this needs to be changed to a while clause, at the moment it'll wait till all 10000 pings are done, I need it to return when the ping is successful. The program "say" is on OSX it makes the computer speak.
#!/bin/bash
echo begin ping
if ping -c 100000 8.8.8.8 | grep timeout;
then echo `say timeout`;
else echo `say the internet is back up`;
fi
OK I don't have rights to answer my own question so here's my answer for it after playing around:
Thanks, yeah I didn't know about $? until now. Anyway now I've gone and made this. I like that yours doesn't go forever but in my situation I didn't need it to stop until it's finished.
#!/bin/bash
intertube=0
echo "begin ping"
while [ $intertube -ne 1 ]; do
ping -c 3 google.com
if [ $? -eq 0 ]; then
echo "ping success";
say success
intertube=1;
else
echo "fail ping"
fi
done
echo "fin script"

Answer 1

You probably shouldn't rely on textual output of a command to decide this, especially when the ping command gives you a perfectly good return value:
The ping utility returns an exit status of zero if at least one response was heard from the specified host; a status of two if the transmission was successful but no responses were received; or another value from <sysexits.h> if an error occurred.
In other words, use something like:
((count = 60)) # Maximum number to try.
while [[ $count -ne 0 ]] ; do
ping -c 1 8.8.8.8 # Try once.
rc=$?
if [[ $rc -eq 0 ]] ; then
((count = 1)) # If okay, flag loop exit.
else
sleep 1 # Minimise network storm.
fi
((count = count - 1)) # So we don't go forever.
done
if [[ $rc -eq 0 ]] ; then # Make final determination.
echo `say The internet is back up.`
else
echo `say Timeout.`
fi

Answer 2

You don't need to use echo or grep. You could do this:
ping -oc 100000 8.8.8.8 > /dev/null && say "up" || say "down"

Answer 3

This can also be done with a timeout:
# Ping until timeout or 1 successful packet
ping -w (timeout) -c 1

Answer 4

I use this Bash script to test the internet status every minute on OSX
#address=192.168.1.99 # forced bad address for testing/debugging
address=23.208.224.170 # www.cisco.com
internet=1 # default to internet is up
while true;
do
# %a Day of Week, textual
# %b Month, textual, abbreviated
# %d Day, numeric
# %r Timestamp AM/PM
echo -n $(date +"%a, %b %d, %r") "-- "
ping -c 1 ${address} > /tmp/ping.$
if [[ $? -ne 0 ]]; then
if [[ ${internet} -eq 1 ]]; then # edge trigger -- was up now down
echo -n $(say "Internet down") # OSX Text-to-Speech
echo -n "Internet DOWN"
else
echo -n "... still down"
fi
internet=0
else
if [[ ${internet} -eq 0 ]]; then # edge trigger -- was down now up
echo -n $(say "Internet back up") # OSX Text-To-Speech
fi
internet=1
fi
cat /tmp/ping.$ | head -2 | tail -1
sleep 60 ; # sleep 60 seconds =1 min
done

Answer 5

If you use the -o option, BSD ping (which is also on macOS) will exit after receiving one reply packet.
Further reading: https://www.freebsd.org/cgi/man.cgi?query=ping
EDIT: paxdiablo makes a very good point about using ping’s exit status to your advantage. I would do something like:
#!/usr/bin/env bash
echo 'Begin ping'
if ping -oc 100000 8.8.8.8 > /dev/null; then
echo $(say 'timeout')
else
echo $(say 'the Internet is back up')
fi
ping will send up to 100,000 packets and then exit with a failure status—unless it receives one reply packet, in which case it exits with a success status. The if will then execute the appropriate statement.

Answer 6

Here's my one-liner solution:
screen -S internet-check -d -m -- bash -c 'while ! ping -c 1 google.com; do echo -; done; echo Google responding to ping | mail -s internet-back my-email#example.com'
This runs an infinite ping in a new screen session until there is a response, at which point it sends an e-mail to my-email#example.com. Useful in the age of e-mail sent to phones.
(You might want to check that mail is configured correctly by just running echo test | mail -s test my-email#example.com first. Of course you can do whatever you want from done; onwards, sound a bell, start a web browser, use your imagination.)

Answer 7

I liked paxdiablo's script, but wanted a version that ran indefinitely. This version runs ping until a connection is established and then prints a message saying so.
echo "Testing..."
PING_CMD="ping -t 3 -c 1 google.com > /dev/null 2>&1"
eval $PING_CMD
if [[ $? -eq 0 ]]; then
echo "Already connected."
else
echo -n "Waiting for connection..."
while true; do
eval $PING_CMD
if [[ $? -eq 0 ]]; then
echo
echo Connected.
break
else
sleep 0.5
echo -n .
fi
done
fi
I also have a Gist of this script which I'll update with fixes and improvements as needed.