preupgrade.jar version number

Mike Dietrich is very motivated to convince everyone who wants to take Oracle database upgrades serious to use always the latest version of preupgrade.jar.

Some parts of Note:884522.1 - How to Download and Run Oracle's Database Pre-Upgrade Utility
 are misleading in my point of view:

If the upgrade-to version is 12.2 or higher, then save the file to your target $ORACLE_HOME/rdbms/admin directory and then unzip the file. It could be your source or target $ORACLE_HOME.

but this will be sorted out for sure in the new future.

For me deploying some files to an ORACLE_HOME (after it's own well defined deployment process) sounds creepy, and I'm interested how this will fit into the concept of read-only ORACLE_HOMEs in 18c+.

As I don't want to modify anything (even replacing with the identical files in case latest preupgrades.jar is deployed already) it's better to check the version of current preupgrade.jar.

If it is used already, the Build number is visible in
preupgrade.log:

Report generated by Oracle Database Pre-Upgrade Information Tool Version
12.2.0.1.0 Build: 14

Upgrade-To version: 12.2.0.1.0

=======================================
Status of the database prior to upgrade
=======================================
...

But if it is not executed (yet), you have to get the Build number from the jar file.
At the moment (Build 014) you can get it from preupgrade_package.sql by a simple statement:

unzip -p $PATH_TO_PREUPGRADE/preupgrade.jar preupgrade_package.sql | \
awk '$1 ~ /c_build/ { print $5 }' | tr -d \;

This can help to identify the current installation and if a (re-)installation is really required.

---

unfortunately there are some inconsistencies.
e.g. in preupgrade_181_cbuild_2_lf.zip:
if you unzip this file you will get a preupgrade_package.sql with c_build is 2
but the preupgrade_package.sql inside of preupgrade.jar shows c_build is 1