# Set environment variables¶

## CLAW¶

To use the Fortran versions of Clawpack you will need to set the environment variable CLAW to point to the top level of clawpack tree (there is no need to perform this step if you will only use PyClaw). In the bash shell these can be set via:

export CLAW=/full/path/to/clawpack  # to top level clawpack directory


## FC¶

You also need to set FC to point to the desired Fortran compiler, e.g.:

export FC=gfortran   # or other preferred Fortran compiler


Consider putting the two commands above in a file that is executed every time you open a new shell or terminal window. On Linux machines with the bash shell this is generally the file .bashrc in your home directory. On a Mac it may be called .bash_profile.

If your environment variable CLAW is properly set, the command

ls \$CLAW


should list the top level directory, and report for example:

README.md       riemann/        pyclaw/
amrclaw/        setup.py        clawutil/
geoclaw/        visclaw/        classic/


## PYTHONPATH¶

We do not recommend setting this environment variable. See Python path for more information. Instead we recommend using pip install to set the Python path appropriately, see pip install instructions.