Setting environment variables

An environment variable is a variable set outside of a program: it is then available to shell commands, Python or R scripts, etc. The benefit of using such variables is that they allow the same code to work in different environments: if BLab share is mounted to Z:\ on one machine, Y:\ on another, and /Volumes/Fas-Phyc-PEB-Lab on yet another one, a program can use the value of the PN_OPUS_PATH environment variable set on each machine to Z:\, Y:\, and /Volumes/Fas-Phyc-PEB-Lab respectively.

On MacOS

The instructions will depend on which shell you are using (run ps -p $$ and look at the CMD column in the output if unsure). For bash, edit ~/.bash_profilen, for zsh, edit ~/.zprofile. In both cases, add the following line to set BLAB_SHARE_PATH to /Volumes/Fas-Phyc-PEB-Lab

export PN_OPUS_PATH=/Volumes/Fas-Phyc-PEB-Lab

On Windows

1. Click on the Start button.

2. Start typing "environment".

3. Select "Edit environment variables for your account" (or something similar, just not something with "the system").

4. Click "New"/"Add".

5. To set PN_OPUS_PATH to Z:\, use PN_OPUS_PATH as the name and Z:\ as the value.

For a terminal session

Run the following command to set BLAB_SHARE_PATH to /Volumes/Fas-Phyc-PEB-Lab

$ export BLAB_SHARE_PATH=/Volumes/Fas-Phyc-PEB-Lab

For a single command

To run a python script called foo.py that resides in the current directory, temporarily setting the environment variable PN_OPUS_PATH to Volumns/pn-schmopus, run

$ PN_OPUS_PATH=/Volumes/pn-schmopus python foo.py