sed and ln commands not working in rpm post install script - sed

Question

I'm trying to build an RPM for our program and running into some issues. I'm trying to run the sed and ln commands as a script in the postinstall/preremove and they don't seem to be making any changes. We are using the maven rpm plugin to build the RPM. I read somewhere that turning selinux off might help but it still doesn't work. We are using CentOS 7.
from the pom.xml:
<postinstallScriptlet>
<script>sed -i 's/foo/bar/g' /path/to/file</script>
</postinstallScriptlet>
<preremoveScriptlet>
<script>sed -i 's/bar/foo/g' /path/to/file</script>
</preremoveScriptlet>
This works when I run it by hand but not as part of the rpm

Answer 1

That should work with fresh install. However it will not work when you are upgrading packages. Because of the ordering. See https://fedoraproject.org/wiki/Packaging:Scriptlets#Scriptlet_Ordering
Rpm first call postinstallScriptlet of new package, install it, and then call preremoveScriptlet of old version of package and then remove the old version.
So you basically call sed -i 's/foo/bar/g' /path/to/file immediatelly followed by sed -i 's/bar/foo/g' /path/to/file.
You likely want something like:
<preremoveScriptlet>
<script>
if [ 0$1 -eq 0 ] ; then
sed -i 's/bar/foo/g' /path/to/file
fi
</script>
</preremoveScriptlet>
which will call the sed only if you are really uninstalling the package. And not during upgrades. Similary for post install scriptlet. See https://fedoraproject.org/wiki/Packaging:Scriptlets#Syntax