tmux - Environment variables don't show up in session

Question

I'm trying to move from screen to tmux (to eventually using tmux from within byobu). However, I have a severe problem with environment variables not being applied, especially PS1. None of them get copied to the session (or window) environments. I found this thread that seemed relevant:

How do I start tmux with my current environment?

However, I actually can see all my right variables when I do

:show-environment -g

But none of them get carried over to the session environment, so I don't see anything when I do

:show-environment

I do have the right update-environment statement in my ~/.tmuxrc file:

# start a non-login shell by default for each new window
set -g default-command 'bash'

# Prefix is C-a like in screen
unbind C-b
set -g prefix C-a

# Carry over the PS1
set-option -ga update-environment "PS1"

Frankly this all seems like a mess to me. I can see the benefit of starting from a clean session for each screen, but for the most part this seems like a pain. I export the variable I intend to use in sub-processes, such as as the Python virtualenvwrapper functions, and expect them to be available.

Is there a way to disable this behavior? If not, what should I try to carry over my PS1 variable to tmux?

EDIT 11/13/2013

I realized that removing the first line (default-command bash) does carry over all of the environment variables. However, I really don't want each new screen of tmux to launch as a login shell. For instance, I specifically declared my PS1 variable in a login shell, so that it wouldn't be overwritten whenever I open a new screen.

Based on the following post, every new screen in tmux should launch as a non-login shell: https://superuser.com/questions/614277/profile-and-bash-profile-ignored-when-starting-tmux-from-bashrc

Why is this not happening by default for me?

sjbx sjbx · Accepted Answer · 2013-11-05T11:33:43

Tmux cannot update running processes (e.g. bash), it can only update its own environment. If you were to start a new window/pane it would pick up the new environment. My suggestion would be to use a utility function like this:

#!/bin/bash

tmup () 
{ 
    echo -n "Updating to latest tmux environment...";
    export IFS=",";
    for line in $(tmux showenv -t $(tmux display -p "#S") | tr "\n" ",");
    do
        if [[ $line == -* ]]; then
            unset $(echo $line | cut -c2-);
        else
            export $line;
        fi;
    done;
    unset IFS;
    echo "Done"
}

This goes through all the updated environment that tmux has learned about and updates your shell.

tmux - Environment variables don't show up in session

1 Answers