script not executing all the way through

Question

I wanted to replace ifplugd with a script, a deamon-like script that will be launched at startup by i3. Everything works fine when launching it from terminal, but whenever i try to auto launch it at startup, it gets killed instantly.

The command i use to launch it as i3 starts up:

exec ./.scripts/ifwatch enp0s25>ifwatch.log

The log file content:

[17:00:54]:Setting enp0s25 up
[17:00:55]:Listening on enp0s25

The script it self:

#!/bin/sh
dev=$1
echo [$(date +'%H:%M:%S')]:Setting $dev up
sudo ip link set $dev up
echo [$(date +'%H:%M:%S')]:Listening on $dev
while watch -n 5 -g ip link show dev $dev;
do
    if [[ -n $(ip link show dev $dev |tr '\n' ' ' | grep -v 'NO-CARRIER') ]];
    then
        echo [$(date +'%H:%M:%S')]:$dev "connected! running dhcpcd"
        echo $(sudo dhcpcd $dev)
    else
        echo [$(date +'%H:%M:%S')]:$dev "disconnected! killing dhcpcd"
        echo $(sudo dhcpcd -k $dev)
    fi

done

I tried to launch it in a screen instance (from the i3config file) but it didn't even created the socket, I also tried not sending the watch output buffer to /dev/null but it didn't help. I'm assuming the process get's instantly killed because at every startup the timestamp of the log file changes.

Answer 1

As Charles Duffy suggested i wrote a function to do the job of watch -g and now it works perfectly. As he said probably watch does not work outside of a TTY.

Here's the code if anyone's intrested:

#!/bin/sh
dev=$1
sleeptime=5

function watcher {
    state1=$(ip link show dev $dev) 
    state2=$state1
    while [ "$state1" == "$state2" ];
    do
        sleep $sleeptime
        state2=$(ip link show dev $dev)
    done
    return 0
}


echo [$(date +'%H:%M:%S')]:Setting $dev up
sudo ip link set $dev up
echo [$(date +'%H:%M:%S')]:Listening on $dev
while watcher;
do
    if [[ -n $(ip link show dev $dev |tr '\n' ' ' | grep -v 'NO-CARRIER') ]];
    then
        echo [$(date +'%H:%M:%S')]:$dev "connected! running dhcpcd"
        sudo dhcpcd $dev
    else
        echo [$(date +'%H:%M:%S')]:$dev "disconnected! killing dhcpcd"
        sudo dhcpcd -k $dev
    fi

done