TMUX setting environment variables for sessions

Question

I work in a situation where I have multiple projects and within each are many scripts that make use of environment variables set to values specific to that project.

What

Answer 1

Example

In my case I'm starting a tmux session per project within a bash script and I needed to activate a relevant virtual environment for that session, including any newly opened tabs. To do so, I added the following virtual environment activation code to the ~/.bashrc:

if [ -n "$VIRTUAL_ENV" ]; then
    source $VIRTUAL_ENV/bin/activate;
fi

However if I need to set foo environment for Session_1 and bar environment for Session_2, the VIRTUAL_ENV variable is globally set to bar after creating Session_2, so any newly opened tabs in Session_1 erroneously ends up in bar environment.

Solution

original HOWTO (commit).

1. Add the following in your ~/.profile (or ~/.bashrc):

# For Tmux VirtualEnv support
tmux_get_var(){
    local key=$1
    [[ -n "$TMUX" ]] && tmux showenv | awk -F= -v key="$key" '$1==key {print $2}'
}

# activate the virtual environment if it is declared
venv=$(tmux_get_var "VIRTUAL_ENV")
if [ -n "$venv" ]; then
    source $venv/bin/activate;
fi

2. Set the VIRTUAL_ENV variable for the target session:

tmux setenv -t ${SESSION_NAME} 'VIRTUAL_ENV' /path/to/virtualenv/