BASH Keep counter through reboots - bash

Question

I'm trying to keep a external counter in my bash script.
As most of the script is specific to what it's for, I'm only going to insert the pertinent parts that I can't seem to get working. Everything before does get defined. Also before someone comments about the cat, I tried (< $TMPFILE) as well. The issue appears to be not writing to the file.
#!/bin/bash
TMPFILE="/tmp/nettestnum"
if [ -e "$TMPFILE" ]; then I=$(cat $TMPFILE); else I="1"; fi
nettest_start() {
grep -q "/root/bin/nettest" /etc/rc.local
if [ $? -eq 1 ]; then
sed -i 's|touch /var/lock/subsys/local|touch /var/lock/subsys/local \&\& /root/bin/nettest|' /etc/rc.local 2>&-
echo "Script started at $DATEVAL" >> "$LOGFILE" 2>&1
echo "Script will run every $TIMELb minutes, $LIMIT times"
touch "$TMPFILE"
nettest_run
else
echo "Nettest is already started and will relaunch upon next reboot"
fi
}
nettest_run() {
echo "$DATE : Starting scan" >> "$LOGFILE" 2>&1
#
while [[ "$I" -lt "$LIMIT" ]]
do
echo "$DATE : Starting scan" >> "$LOGFILE" 2>&1
#
HOSTS="$(...)"
for myHost in $HOSTS
do
PING=$(ping -f -c $COUNT "$myHost" |grep 'rtt' | awk '{print $4}')
echo "$myHost / $PING" >> "$LOGFILE" 2>&1
done
echo "$DATEVAL : Finished" >> "$LOGFILE" 2>&1
echo "$DATEVAL : Netstat Start" >> "$STATLOG" 2>&1
netstat -s |egrep -i "dropped|loss|reject|timeout|invalid" >> "$STATLOG" 2>&1
echo "$DATEVAL : Netstat Finished" >> "$STATLOG"G 2>&1
echo "." >> "$LOGFILE" 2>&1
sleep "$TIMEL"
let I++ || true
set +C
echo "$I" > "$TMPFILE"
done
}
Edit 4: re-added } and showing both functions.
I also need to figure out how to write an exit for the loop, but I'm pretty sure that's just a [ $? = 0 ]
Edit:
An example of some of the output I'm seeing when I run a status command (built into the script)..
Nettest is enabled on startup
PID number: 6059
Nettest is actively running in memory
On iteration of 100
iteration shows 1 on the first run.
Edit 2: redid the sample with full example, minus customized commands.

Answer 1

In the end, I got it working by adding 2>&1 to the line needed.
echo "$I" > "$TMPFILE" 2>&1

Answer 2

Try this:
if [ -e "$TMPFILE" ]; then I=`cat $TMPFILE`; else I=1; fi
while [[ $I -lt $LIMIT ]]

Answer 3

A while loop creates a subshell, with a copy of all your current variables.
#!/bin/bash
I=1
CHECK=1 # boolean for demonstration
while CHECK; do
let I++
CHECK=0
done
echo $I # prints 1, not two
This happens because the while subshell gets a copy of the I variable, which it increments. Once the subshell exits, the original variable comes back.
Your I variable is being incremented, and acting as your loop counter. I expect this is causing you all kinds of problems for properly ending your loop, and having other bits of this program see the "right" variable. I see no reason you could not replace the while loop with an equivalent for loop, and avoid all of these problems entirely.