How to find version of CUDA

Users of CUDA usually know its major.minor version.

If you want to know the full major.minor.patch version of CUDA you are using:

$ cat /usr/local/cuda/version.txt

For example, when I tried on my CUDA 9.2 installation:

$ cat /usr/local/cuda-9.2/version.txt                                                                                                                                                                        
CUDA Version 9.2.148