Environment variables

A tool session sets a number of environment variables. The useful ones are below; env in a session terminal lists them all.

A tool runs as the member who launched it, with that member's permissions. That is why it can write to their home directory.

Variable	Value	What it is for
SESSION	The session number	Identifies the running session. It also appears in the browser URL of the session.
USER	The member's username	The account the tool runs as.
SESSIONDIR	/home/<hubname>/<username>/data/sessions/<session>	A directory of its own for each session. The working directory a tool starts in, and the right place for temporary files.
RESULTSDIR	/home/<hubname>/<username>/data/results/<session>	Where to leave results the member will want after the session ends.
PWD	The present working directory	Standard shell variable.
HOME	/home/<hubname>/<username>	The member's home directory.

Both SESSIONDIR and RESULTSDIR count against the member's storage quota.

If a tool saves work outside the session, put it under a directory of its own — $HOME/data/<toolname> — rather than scattering files across the home directory. Unlike SESSIONDIR and RESULTSDIR, that directory is not created for you.

Rappture writes its results to RESULTSDIR. Rappture is deprecated; on most hubs a Jupyter notebook is the current path. See Jupyter Notebooks, whose environment variables page covers the same variables from a notebook.