check for device connectivity on network then send action based on connectivity - bash

Question

I am fairly new to bash script even though I have some experience.
I am looking for my Raspberry Pi to detect my phone when it becomes available on the network, when it does so to play an audio clip, I have managed do this via the script below.
I have a problem, however, when my phone becomes available on the network, I do not want the audio to keep looping; I need it to play once and then stop playing the audio clip once it has already played. However, I do want the script to keep on running so it can detect the next time my phone becomes available on the network.
Maybe there is a better way of doing it, if there is I would love to hear your suggestions.
#!/bin/sh
if ping -c 10 192.168.1.4 &> /dev/null
then
kodi-send --action="PlayMedia(/storage/music/welcome.mp3)"
ping 192.168.1.4 &> /dev/null
else
./checkforerikphone.sh
fi

Answer 1

try this
#!/bin/bash
while : ; do
if ping -c 10 192.168.1.4 &> /dev/null ; then
kodi-send --action="PlayMedia(/storage/music/welcome.mp3)"
fi
sleep 600
done
This solution runs forever while :. and every 10 minutes, checks if your phone is active. So this significantly reduces the noise in your life, but it also lets you know that your phone is still connected.
You could change sleep 600 to sleep 300 and check every 5 minutes, or of course you can change 600 to any number of seconds you comforatable with.
Not a perfect solution per your spec, but managing lock files can be complicated.
Get comfortable with this solution and then think about adding something like
if ping ... ; then
if ! [[ -e /tmp/phoneOnLine ]] ; then
kodi-send ...
echo "Found phone at $(date)" > /tmp/phoneOnLine
fi
else
echo "no phone found"
/bin/rm -f /tmp/phoneOnLine
fi
You will definitely find corner cases where this doesn't work, so be prepared to debug the code. I would add an echo msg inside of each logic path (if/else/...). to understand how the code is working.
Also to prevent script for being faked out, I would delete the file at startup.
So a possible complete solution is
#!/bin/bash
#file may not exist, ignore error msg with "2> /dev/null"
/bin/rm -f /tmp/phoneOnLine 2> /dev/null
#loop forever
while : ; do
# check for phone
if ping -c 10 192.168.1.4 &> /dev/null ; then
# check for "lock" file
if ! [[ -e /tmp/phoneOnLine ]] ; then
kodi-send --action="PlayMedia(/storage/music/welcome.mp3)"
echo "Found phone at $(date)" > /tmp/phoneOnLine
else
echo "Phone already found"
fi # !! -e /tmp/ph
else # no ping
echo "no phone found"
/bin/rm -f /tmp/phoneOnLine 2>/dev/null
fi # ping
sleep 600
done

Answer 2

Try following:
#!/bin/bash
#when result of ping $? is 0, the phone is detected
ACTIVE=0
#default startup as NOT ACTIVE(not detected) => !0
pre_available=1
# loop forever
while :
do
#ping and store outcome in "available"
ping -c 10 192.168.0.8 > /dev/null
available=$?
#if phone was not active and just got active (detected)
if [[ "$pre_available" != "$ACTIVE" && "$available" == "$ACTIVE" ]]
then
#do your stuff
kodi-send --action="PlayMedia(/storage/music/welcome.mp3)"
fi
#store availability for next iteration
pre_available=$available
done