Usable Variables (Other than ones in customize.sh)
MODPATH - Working directory of installer - where all files are extracted to - currently equivalent to /data/adb/modules_update/$MODID
MODID - 'id' from module.prop - the unique identifier for your mod
MODULEROOT - The directory containing MODPATH (currently /data/adb/modules_update)
NVBASE - if magisk install - path to magisk files (currently /data/adb)
LIBDIR - If DYNAMICLIB=true: Equal to /system/vendor if rom is oreo+, /system otherwise
LIBPATCH - Same as libdir but formatted for sed with standard '/' delimiter
API - Taken from build.prop. Equal to the API level (android version) of the device (e.g. 21 for Android 5.0)
ABI - Taken from build.prop. Equal to the cpu architecture of the device - equal to arm, arm64-v8a, x86 or x86_64
ARCH - Truncated form of ABI - equal to arm, arm64, x86, or x86_64
ARCH32 - Equal to the simplified cpu type of the device (useful for differentiating between 32 and 64bit cpus) - equal to arm or x86
IS64BIT - Set to 'true' if 64 bit capable device is detected, set to 'false' otherwise
ORIGDIR - The original directory for device files (original files unaffected by magisk mounting). Equals $INTERNALDIR/mirror (INTERNALDIR=$(magisk --path)/.magisk). This is useful if you're copying files from the device to your mod for modification.
EXTRAPART - true if KSU or magisk delta detected (support extra partitions like odm), false otherwise
Variables for uninstall.sh and boot scripts (differ slightly from main installer ones)
MODID - Same as before
LIBDIR - Same as before
INFO - Equal to the INFO file (contains a list of all installed files not in magisk mod directory)
MODPATH - Equal to module directory
MODDIR - Equal to current directory, will be different that $MODPATH if script isn't installed in $MODPATH directory (such as with .core scripts)