How to exit with exit code from pkg installer

Maybe use an if else conditional statement.

As for grabbing the correct exit code, I suspect you could grep it from install.log but I can’t see what you’re looking at.

if [ -x /Applications/program.app ]; then
echo “App exists”
exit 0
else
echo “App doesn’t exist”
fi

exit 1

Taking a couple of steps back here, why does this installer need to be installed from that specific location? You may want to dig into this a bit to understand why it requires this. For example, does it need to be able to see a configure file in the same location when it's being installed? If so, there are other ways to approach this so you don't have to jump through all these hoops to get their wares installed.

you could try running your package like this : 

pkgexitcode=$(installer -pkg /Library/Application\\ Support/TheApp/installer.pkg -target /)

exitcode=$pkgexitcode