[Q] [RECOVERY][ZIP]script lines for copy, move, rename files. - Android Q&A, Help & Troubleshooting

So as I see in a flashable zip there is:
META-INF\com\google\android\
where you have updater-script.
Mine contains this:
ui_print("text_to_write");
run_program("/sbin/busybox", "mount", "/cache");
run_program("/sbin/busybox", "mount", "/data");
run_program("/sbin/busybox", "mount", "/system");
ui_print("");
package_extract_dir("cache", "/cache");
package_extract_dir("data", "/data");
package_extract_dir("system", "/system");
unmount("/cache");unmount("/data");
unmount("/system");
ok, basically this mounts the cache, data, system partition.
Now I want to do something like:
got a file in /system/media/sounds/ui/lock.ogg
I want it to rename it to /system/media/sounds/ui/lock.ogg.back
as I searched the forum, I need to run a bash script, something like:
for file in *.html; do
mv "$file" "`basename $file .html`.txt"
or simply
mv Lock Lock_old
now my question
what to write in update script to rename these files before copying the actual files.
What to write in the the update-script to run the bash.
as I understand I should paste a new line
run_program("/sbin/busybox", "mount", "/system");
ui_print(""); <-right here the script line
package_extract_dir("cache", "/cache");
the main goal is this:
copy for example Lock.ogg to system/media/ui/
but before copying rename the existing Lock.ogg to Lock.ogg.back or Lock_old.ogg.
Please help