How to check running Raspberry Pi OS version, 32 bit or 64 bit.

To check the bit size (32 bit or 64 bit) of the running Raspberry Pi OS, you can enter the commands:

$ uname -m

aarch64

or:

$ arch

aarch64

You can also check the bit size of the Linux kernel with:

$ getconf LONG_BIT

64

Tested on Raspberry Pi 4B running Raspberry Pi OS 64-bit (bullseye):

Tested on Raspberry Pi 4B running Raspberry Pi OS 32-bit (buster):