Show unique SSH sessions upon login

[maxwellmlin]

Motivation

Problems have arisen when multiple people SSH into the robot and work on different issues. We need an indicator that informs the user the current number of unique and active SSH sessions.

Notes

This is currently appended to ~/.profile of the robot computer:

echo "Active pts sessions (only counts Macs): $(who -a | grep "+ pts" | wc -l)"

Unfortunately, this seems to only echo pts sessions started by Mac computers (tested using 2 Macs, 2 Windows). Additionally, pts does not just include SSH connections but also pseudo-terminal devices such as xterm or screen.

Ideally, we want to echo the current number of unique and active sessions.

[vedarshshah]

This hasn't been an issue recently. We've been communicating with each other whenever someone's SSH'd into the robot and ensuring we don't have overlapping changes.