Why are you trying to capture the SN, JAMF Assigned user name, IP, and user name at each log in? JAMF Already captures all this information from macOS's logs.
If you must do this, I would recommend making it a launchdaemon and cut JAMF out of it. Also >> will not create a directory, so if /usr/local/bin/logs does not exist it will error out. I would also replace $3 with a function to grab the logged in user from the Mac rather than JAMF.
Something like this may work better. Also do not use 777 as that is world writable, this is just for a simple example.
#!/bin/bash
username=`/bin/ls -l /dev/console | /usr/bin/awk '{ print $3 }' | tr "[a-z]" "[A-Z]"`
serialnumber="$(ioreg -c IOPlatformExpertDevice -d 2 | awk -F\" '/IOPlatformSerialNumber/{print $(NF-1)}')"
ip="$(ifconfig | grep 'inet 10' | grep -m1 -o '\d\{1,3\}\.\d\{1,3\}\.\d\{1,3\}\.\d\{1,3\}' | grep -m1 '10')"
if [ -d "/usr/local/bin/Logs" ]
then
echo '/usr/local/bin/Logs/ Exists, writing log'
sudo echo ${username} >> /usr/local/bin/Logs/logs.txt
sudo echo ${serialnumber} >> /usr/local/bin/Logs/logs.txt
sudo echo ${ip} >> /usr/local/bin/Logs/logs.txt
else
echo '/usr/local/bin/Logs/ does not exist, creating directory'
sudo mkdir "/usr/local/bin/Logs/"
sudo chmod 777 "/usr/local/bin/Logs/"
sudo echo ${username} >> /usr/local/bin/Logs/logs.txt
sudo echo ${serialnumber} >> /usr/local/bin/Logs/logs.txt
sudo echo ${ip} >> /usr/local/bin/Logs/logs.txt
fi
