I daily use tmux (2.5) on my laptop to work, and my tmux sessions have a starting directory which is the working directory I started the tmux session from. Every pane/window I open start with this starting directory as working directory.
I can change this starting directory, and this change would apply to the whole session.
But if I want to work on a different project with several panes, I could start a new window, but every pane I would open in it would start with the session's starting directory : I would have to cd to the new location for each pane which isn't practical.
If I need to work on several project/directories simultaneously, I can start a new terminal session, then cd to the relevant directory/project and start a new tmux session. That's not complicated.
But if I want to do the same thing on a server through ssh, I'd need to either :
open a new ssh session.
either embed my remote tmux sessions in an other tmux session.
Neither sounds practical to me, I'd prefer a single tmux session on the remote machine.
I think it would be more convenient to being able to start new window with its own starting directory location that would apply to any new pane opened in it. Is there a way to achieve this?
Edit :
I already tried the -c parameter of tmux new-window command.
But it doesn't assign its starting directory to the window created this way, it only applies this custom starting directory to the first pane created.
Any new pane opened in this window then uses the session's starting directory as default working dir (and not the path passed to tmux new-window).
This question is very similar to: https://unix.stackexchange.com/questions/12032/create-new-window-with-current-directory-in-tmux
It depends on your tmux version but the -c parameter does do the trick but it does not remember the setting. There used to be a default-path setting but that has been removed in version 1.9 unfortunately.
For newer versions you will need to pass along the -c in all cases (you can use an alias if you manually execute that command) or if you use key bindings you need to rebind the split/new window keys.
bind '"' split-window -c "#{pane_current_path}"
bind % split-window -h -c "#{pane_current_path}"
bind c new-window -c "#{pane_current_path}"
To use a custom path instead of the current pane path, execute this command:
tmux setenv custom_path /home/whatever/some/path
Put this in your config:
bind '"' split-window -c "#{custom_path}"
bind % split-window -h -c "#{custom_path}"
bind c new-window -c "#{custom_path}"
Yes, it turns out the -c option to the new-window command is what you are looking for: https://unix.stackexchange.com/questions/12032/create-new-window-with-current-directory-in-tmux Also, this: https://unix.stackexchange.com/questions/101949/new-tmux-panes-go-to-the-same-directory-as-the-current-pane-new-tmux-windows-go
So either of tmux new-window -c $(pwd) or tmux new-window -c /path/to/dir inside your tmux session should do it.
Related
I am trying to find a nice way to restore the SSH agent when I reconnect a disconnected tmux session.
The cause seems to be that the SSH agent session changes but the environment variable from the tmux session is not updated.
How can I automate this, before attaching the session itself? Because the session I am attaching to does not always have a bash prompt, so I cannot afford to type something inside it. It has to be something to run before creating or attaching the tmux session.
An example of the code I'm running is at https://gist.github.com/ssbarnea/8646491 -- a small ssh wrapper that is using tmux to create persistem ssh connections. This works quite well, but sometimes the ssh agent stops working so I am no longer able to use it to connect to other hosts.
There's an excellent gist by Martijn Vermaat, which addresses your problem in great depth, although it is intended for screen users, so I'm adjusting it for tmux here.
To summarize:
create ~/.ssh/rc if it doesn't exist yet, and add the following content:
#!/bin/bash
# Fix SSH auth socket location so agent forwarding works with tmux.
if test "$SSH_AUTH_SOCK" ; then
ln -sf $SSH_AUTH_SOCK ~/.ssh/ssh_auth_sock
fi
Make it work in tmux, add this to your ~/.tmux.conf:
# fix ssh agent when tmux is detached
setenv -g SSH_AUTH_SOCK $HOME/.ssh/ssh_auth_sock
Extra work is required if you want to enable X11 forwarding, see the gist.
While tmux updates SSH variables by default, there is no need to
change/add socket path
change the SSH_AUTH_SOCKET variable
I like the solution by Chris Down which I changed to add function
fixssh() {
eval $(tmux show-env \
|sed -n 's/^\(SSH_[^=]*\)=\(.*\)/export \1="\2"/p')
}
into ~/.bashrc. Call fixssh after attaching session or before ssh/scp/rsync.
Newer versions of tmux support -s option for show-env, so only
eval $(tmux show-env -s |grep '^SSH_')
is possible.
Here's what I use for updating SSH_AUTH_SOCK inside a tmux window (based on Hans Ginzel's script):
alias fixssh='eval $(tmux showenv -s SSH_AUTH_SOCK)'
Or for tmux that does not have showenv -s:
alias fixssh='export $(tmux showenv SSH_AUTH_SOCK)'
Here is my solution which includes both approaches, and does not require extra typing when I reconnect to tmux session
alias ssh='[ -n "$TMUX" ] && eval $(tmux showenv -s SSH_AUTH_SOCK); /usr/bin/ssh'
There are lots of good answers here. But there are cases where tmux show-environment doesn't see SSH_AUTH_SOCK. In that case you can use find to locate it explicitly.
export SSH_AUTH_SOCK=$(find /tmp -path '*/ssh-*' -name 'agent*' -uid $(id -u) 2>/dev/null | tail -n1)
That's long and complicated, so I'll break it down...
01 export SSH_AUTH_SOCK=$(
02 find /tmp \
03 -path '*/ssh-*'
04 -name 'agent*'
05 -uid $(id -u)
06 2>/dev/null
07 | tail -n1
08 )
export the SSH_AUTH_SOCK environment variable set to the output of the $() command substitution
find files starting in /tmp
limit results to only those with /ssh- in the path
limit results to only those whose name begins with agent
limit results to only those with a user id matching the current user
silence all (permissions, etc.) errors
take only the last result if there are multiple
You may be able to leave off 6 & 7 if you know that there will only be 1 result and you don't care about stderr garbage.
I use a variation of the previous answers:
eval "export $(tmux show-environment -g SSH_AUTH_SOCK)"
assuming that you did the ssh agent started from the outer environment. Same goes for other environment variables such as DISPLAY.
I prefer to avoid configuring TMUX (etc) and keep everything purely in ~/.ssh/. On the remote system:
Create ~/.ssh/rc:
#!/bin/bash
# Fix SSH auth socket location so agent forwarding works within tmux
if test "$SSH_AUTH_SOCK" ; then
ln -sf $SSH_AUTH_SOCK ~/.ssh/ssh_auth_sock
fi
Add following to ~/.ssh/config so it no longer relies on $SSH_AUTH_SOCK, which goes stale in detached terminals:
Host *
IdentityAgent ~/.ssh/ssh_auth_sock
Known limitations
ssh-add doesn't use ~/.ssh/config and so cannot communicate with ssh-agent. Commands like ssh-add -l produce errors, even though ssh user#host works fine, as does updating git remotes which are accessed via SSH.
I may have worked out a solution that is fully encapsulated in the ~/.tmux.conf configuration file. It is a different approach than modifying the ~/.bash_profile and ~/.ssh/rc.
Solution only using ~/.tmux.conf
Just cut and paste the following code into your ~/.tmux.conf
# ~/.tmux.conf
# SSH agent forwarding
#
# Ensure that SSH-Agent forwarding will work when re-attaching to the tmux
# session from a different SSH connection (after a dropped connection).
# This code will run upon tmux create, tmux attach, or config reload.
#
# If there is an SSH_AUTH_SOCK originally defined:
# 1) Remove all SSH related env var names from update-environment.
# Without this, setenv cannot override variables such as SSH_AUTH_SOCK.
# Verify update-environment with: tmux show-option -g update-environment
# 2) Force-set SSH_AUTH_SOCK to be a known location
# /tmp/ssh_auth_sock_tmux
# 3) Force-create a link of the first found ssh-agent socket at the known location
if-shell '[ -n $SSH_AUTH_SOCK ]' " \
set-option -sg update-environment \"DISPLAY WINDOWID XAUTHORITY\"; \
setenv -g SSH_AUTH_SOCK /tmp/ssh_auth_sock_tmux; \
run-shell \"ln -sf $(find /tmp/ssh-* -type s -readable | head -n 1) /tmp/ssh_auth_sock_tmux\" \
"
Caveat
The above solution along with the other solutions are susceptible to a race condition when initiating multiple connections to the same machine. Consider this:
Client 1 Connect: SSH to machineX, start/attach tmux (writes ssh_auth_sock link)
Client 2 Connect: SSH to machineX, start/attach tmux (overwrites ssh_auth_sock link)
Client 2 Disconnect: Client 1 is left with a stale ssh_auth_sock link, thus breaking ssh-agent
However, this solution is slightly more resilient because it only overwrites the ssh_auth_sock link upon tmux start/attach, instead of upon initialization of a bash shell ~/.bash_profile or ssh connection ~/.ssh/rc
To cover this last race condition, one may add a key binding to reload the tmux configuration with a (Ctrl-b r) key sequence.
# ~/.tmux.conf
# reload config file
bind r source-file ~/.tmux.conf
From within an active tmux session, executing this sequence when the ssh_auth_sock link goes stale will refresh the ssh-agent connection.
In case other fish shell users are wondering how to deal with this when using fish (as well as for my future self!). In my fish_prompt I added a call to the following function:
function _update_tmux_ssh
if set -q TMUX
eval (tmux show-environment SSH_AUTH_SOCK | sed 's/\=/ /' | sed 's/^/set /')
end
end
I suppose that more advanced *nix users would know how to replace sed with something better, but this works (tmux 3.0, fish 3.1).
Following up on #pymkin's answer above, add the following, which worked with tmux 3.2a on macOS 11.5.3:
To ~/.tmux.conf:
# first, unset update-environment[SSH_AUTH_SOCK] (idx 3), to prevent
# the client overriding the global value
set-option -g -u update-environment[3]
# And set the global value to our static symlink'd path:
set-environment -g SSH_AUTH_SOCK $HOME/.ssh/ssh_auth_sock
To ~/.ssh/rc:
#!/bin/sh
# On SSH connection, create stable auth socket path for Tmux usage
if test "$SSH_AUTH_SOCK"; then
ln -sf "$SSH_AUTH_SOCK" ~/.ssh/ssh_auth_sock
fi
What's going on? Tmux has the semi-helpful update-environment variable/feature to pick up certain environment variables when a client connects. I.e. when you do tmux new or tmux attach, it'll update the tmux environment from when you ran those commands. That's nice for new shells or commands you run inside tmux afterwards, but it doesn't help those shells you've started prior to the latest attach. To solve this, you could use some of the other answers here to have existing shells pick up this updated environment, but that's not the route I chose.
Instead, we're setting a static value for SSH_AUTH_SOCK inside tmux, which will be ~/.ssh/ssh_auth_sock. All shells inside tmux would pick that up, and never have to be updated later. Then, we configure ssh so that, upon connection, it updates that static path with a symlink to the latest real socket that ssh knows.
The missing piece from #pymkin's answer is that Tmux will have the session value override the global value, so doing set-environment -g isn't sufficient; it gets squashed whenever you re-attach. You also have to also tell tmux not to update SSH_AUTH_SOCK in the session environment, so that the global value can make it through. That's what the set-option -g -u is about.
After coming across so many suggestions, I finally figured out a solution that enables TMUX update the stale ssh agent after being attached. Basically, both the zshrc files on the local and remote machines need to be modified.
Insert the following codes into the local zshrc, which is based on this reference.
export SSH_AUTH_SOCK=~/.ssh/ssh-agent.$(hostname).sock
ssh-add -l 2>/dev/null >/dev/null
# The error of executing ssh-add command denotes a valid agent does not
# exist.
if [ $? -ge 1 ]; then
# remove the socket if it exists
if [ -S "${SSH_AUTH_SOCK}" ]; then
rm "${SSH_AUTH_SOCK}"
fi
ssh-agent -a "${SSH_AUTH_SOCK}" >/dev/null
# one week life time
ssh-add -t 1W path-to-private-rsa-file
fi
Insert the following code into the remote zshrc, where the tmux session will be attached.
alias fixssh='eval $(tmux showenv -s SSH_AUTH_SOCK)'
Then ssh into the remote machine. The -A option is necessary.
ssh -A username#hostname
Attach the TMUX session. Check the TMUX evironment variables
# run this command in the shell
tmux showenv -s
# or run this command after prefix CTRL+A or CTRL+B
:show-environment
Run fixssh in the previously existed panes to update the ssh agent. If a new pane is created, it will automatically get the new ssh-agent.
Here's another simple Bash solution, using PROMPT_COMMAND to update the SSH_* vars inside tmux before each prompt is generated. The downside to this solution is that it doesn't take effect in existing shells until a new prompt is generated, because PROMPT_COMMAND is only run before creating new prompts.
Just add this to your ~/.bashrc:
update_tmux_env () {
# Only run for shells inside a tmux session.
if [[ -n "$TMUX" ]]; then
eval $(tmux show-env -s | grep '^SSH_')
fi
}
export PROMPT_COMMAND=update_tmux_env
Here's a new fix to an old problem: I think it's simpler than the other fixes and there's no need to make a static socket or mess with the shell prompt or make a separate command you have to remember to run.
I added this code added to my .bashrc file:
if [[ -n $TMUX ]]; then
_fix_ssh_agent_in_tmux () { if [[ ! -S $SSH_AUTH_SOCK ]]; then eval export $(tmux show-env | grep SSH_AUTH_SOCK); fi }
ssh () { _fix_ssh_agent_in_tmux; command ssh $#; }
scp () { _fix_ssh_agent_in_tmux; command scp $#; }
git () { _fix_ssh_agent_in_tmux; command git $#; }
rsync () { _fix_ssh_agent_in_tmux; command rsync $#; }
fi
If the shell is running within tmux, it redefines 'ssh' and its ilk to bash functions which test and fix SSH_AUTH_SOCK before actually running the real commands.
Note that tmux show-env -g also returns a value for SSH_AUTH_SOCK but that one is stale, I assume it's from whenever the tmux server started. The command above queries the current tmux session's environment which seems to be correct.
I'm using tmux 2.6 (ships with with Ubuntu 18.04) and it seems to work well.
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 i'd like to do is use a separate tmux session for each project and set the variables so that they are set for all windows in that session.
I tried to use the set-environment option which works using the -g option but then sets the variable for all sessions connected to that server.
Without the -g option I see its set when using show-environment but can't access the variable in the shell.
Has anyone come up with a way of fixing this?
Using tmux 1.8 and tcsh
I figured out a way to do this. I'm using tmux 2.5.
Background
In the tmux man page, it states that there are two groups of environment variables: global and per-session. When you create a new tmux session, it will merge the two groups together and that becomes the set of environment variables available within the session. If the environment variables get added to the global group, it appears that they get shared between all open sessions. You want to add them to the per-session group.
Do this
Step 1: Create a tmux session.
tmux new-session -s one
Step 2: Add an environment variable to the per-session group.
tmux setenv FOO foo-one
This adds the environment variable to per-session set of environment variables. If you type tmux showenv, you'll see it in the output. However, it isn't in the environment of the current session. Typing echo $FOO won't give you anything. There's probably a better way to do this, but I found it easiest to just export it manually:
export FOO='foo-one'
Step 3: Create new windows/panes
Now, every time you create a new window or pane in the current session, tmux will grab the FOO environment variable from the per-session group.
Automating it
I use bash scripts to automatically create tmux sessions that make use of these environment variables. Here's an example of how I might automate the above:
#!/bin/bash
BAR='foo-one'
tmux new-session -s one \; \
setenv FOO $BAR \; \
send-keys -t 0 "export FOO="$BAR C-m \; \
split-window -v \; \
send-keys -t 0 'echo $FOO' C-m \; \
send-keys -t 1 'echo $FOO' C-m
You can access tmux (local) environment variables for each session, while in a session, with the command:
bash> tmux show-environment
If you add the -g parameter you get the environment for all sessions, i.e. the global environment. The local environments are NOT the same as the global environment. The previous command prints the entire local environment, but you can also look at just one variable:
bash> tmux show-environment variable_name
variable_name=value
To get the value, you could use some 'sed' magic or use 'export' on a single variable, or you can even 'export' the entire environment to your shell. Below are the 3 approaches.
bash> tmux show-environment variable_name | sed "s:^.*=::"
value
bash> eval "export $(tmux show-environment variable_name)"
bash> echo $variable_name
value
bash> for var in $(tmux show-environment | grep -v "^-"); do eval "export $var"; done;
bash> echo $variable_name
value
If needed, you can just add the -g parameter after the show-environment command if you want to access the global environment.
I've done a simple
export MY_VAR="some value"
before I start the tmux session, which gives me access to MY_VAR from all windows inside that session.
Version 3.2 of tmux will support a -e option for the new-session command for altering the local environment directly.
In the mean time, you can use this to run a new tmux session with a particular environment available and up to date (or one of the other solutions mentioned):
tmux new-session 'export MY_VAR=value; exec bash'
The problem with tmux is that when you first run it, the tmux server is created and it inherits the environment that is available at this time of creation. This is called the global environment. When you run tmux again and create a new session, the tmux server still holds its copy of the environment. But this copy is the "old" environment that the server learned about when it was created, i.e. the global environment.
About the tmux commands that work with the tmux environment:
set update-environment MY_VAR: this will tell tmux to take the MY_VAR variable from the global environment and make it a session environment, i.e. a local environment (listed by the show-environment command). Then, the session will be able to change the value of this variable without affecting the global environment.
set-environment MY_VAR value: This will create (or change) a variable in the local environment of the session.
set-environment -g MY_VAR value: This will create (or change) a variable in the global environment.
Also, note that when you run tmux and tmux calls bash (or another shell), bash will have a copy of the server's (global) environment. Even if you change an environment variable before calling tmux, creating a new session will be oblivious of the changes. If you add a tmux command in a conf file and run tmux e.g. with tmux source-file tmux-session.conf, any variable you mention in the conf will be evaluated in the context of the global environments the tmux server knows about and not the in the context from where you run the tmux command. So, in order to make a new session see the new value of the variable, you have to call tmux in a way that passes the new value of the env variable directly to it. This is what the solutions here try to do. This is also what the new -e option will allow you to do.
I approached this a little differently, assuming I had separate initialization scripts for each environment.
Using tmux v3.0a.
The spec:
When I invoke tmux I want it to load up a specific environment for that session.
For each window within the tmux session I want that same environment session replicated.
I also want to be able to invoke subsequent tmux sessions with different environments and each window invocation should load that environment. (just like the first session) And subsequent sessions should not interfere with prior sessions.
I have shell scripts to initialize each of my environments.
So how can I associate a shell script with a session and have all window invocations use that shell script?
Simple Solution:
Found a simple solution here: How to start two tmux sessions with different environments?
With my original solution I ran into an issue with the tmux global environment. When I ran multiple sessions, whichever one ran first set the global environment. Then I would need to close other tmux sessions before I ran new sessions.
A better solution is to set up a separate tmux server for each environment.
Use the -L flag to tmux from within a shell that already has the environment defined you want.
Shell environment A: tmux -L environA
Shell environment B: tmux -L environB
Name your environments any way you want. Set up some aliases for each environment? Or you can test environment variables to determine which tmux server you want to use. Each tmux named server will keep its environment separate.
Then there is no need to set bash startup files, etc. as I had described in my original solution.
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).
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
Set the VIRTUAL_ENV variable for the target session:
tmux setenv -t ${SESSION_NAME} 'VIRTUAL_ENV' /path/to/virtualenv/
Setting it for current session is quite easy: Ctr-b: to open tmux command prompt and enter setenv FOO foo. This will not apply for existing windows -- but there you can use export $(tmux show-env FOO).
For new sessions this pattern might be useful:
tmux new -s session
Ctr-b : set-env FOO foo -- set FOO=foo for the session
Ctr-b c -- create new, second window ($FOO is set here)
Ctr-b l -- go to old, first window
exit the first window
all windows now have FOO=foo
Tested with Tmux 1.8.
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?
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.
I want to split the current tmux window and have it inherit my current environment.
I need to do this programmatically so I can't do it through some predefined config file.
Simply put, I want to do something like,
tmux split-window my-binary
my-binary is in my current PATH but not the usual one (it seems tmux just goes through my bash_profile).
Is it possible? Or do I have to start bash and setup the env before starting my-binary?
To split a window that will run an instance of your default shell, use the env command that runs whatever is configured as default-command in your ~/.tmux.conf:
tmux split-window "env FOO=bar $(tmux show-options -vg default-command)"
I wonder is there any easy way that I can change an bash environment variable and apply to windows in a tmux session?
I've googled and didn't found a solution so I post the question here.
Thanks!!
You can't directly change the environment variables.
However, you can make shell terminals inside a tmux instance pick up new variables. This requires a few steps.
First, tmux can update environment variables in itself. The update-environment configuration directive does this. Any variable listed here will be auto-udpated - connecting to a tmux session updates the session's environment variable with the value from the client you just connected. So if you run tmux attach, and have SSH_AUTH_SOCK set, then the tmux session will get the new value of SSH_AUTH_SOCK.
However, that only updates the session's variables, so only new panes/windows will get the values. Existing windows will still have the old values. As #IgnacioVazquez-Abrams said, there is not a direct fix to this.
However, you can fix it in many programs. Sufficiently recent versions of tmux have a show-environment command, which queries the session for the current values of an environment variable. This allows you to get the environment variable from within a program after it has been with the update-environment logic.
For instance, you can have some shells pick up the new value. In ZSH, I do this with a precmd hook in ~/.zshrc:
_update_ssh_agent() {
local var
var=$(tmux show-environment |grep '^SSH_AUTH_SOCK=')
if [ "$?" -eq 0 ]; then
eval "$var"
fi
}
if [[ -n "$TMUX" ]]; then
add-zsh-hook precmd _update_ssh_agent
fi
This makes it so that shells inside tmux sessions update the SSH agent every time they go to display a new prompt. After I reconnect, all I have to do is hit enter at a prompt and it grabs the new SSH agent connection.
Bash also has a pre-command mechanism, although I do not know how to configure it off-hand. You could additionally configure more programs to use show-environment to update themselves, such as vim or emacs. However, you will need to configure each program you might want to do this with separately.
No.
And there isn't even a hard way; manipulating the environment variables of another process is non-portable at best.
So this is an old question, but came up when I was searching for what I wanted to do, so here's another solution.
When tmux is started, it copies the environment into a global environment. When new windows are created, it merges the global environment with the session environment to set the environment for that window. We can view these environments with:
tmux show-environment [-g] [-t target-session]
Even better, we can also update the environments, even from within the windows' own tmux session:
tmux set-environment [-gru] [-t target-session] name [value]
For a full explanation of the flags, see the tmux man page.
This feature was exactly what I wanted. Unfortunately it won't update the environment of existing shells, but we could easily loop over tmux showenv -g to re-export the tmux environment that might be set by another process.
Here was my use-case:
With the way I have my shell configuration set up, I export my environment in a login shell, and then exec into a tmux session. I figure since env vars don't change often, I don't need to source them in new non-login shells every time. However, when they do change, I don't want to restart my entire tmux session to have new tmux windows know about the change. While using the update-environment option and re-attaching solves a session restart, it's cumbersome to maintain an explicit list of potentially malleable env vars in my tmux configuration.
With the following function, we can update our environment variables in something like ~/.shenv for example, and instead of sourcing the file (. ~/.shenv), we can promote the file (promote ~/.shenv) for new tmux windows to inherit from this updated environment.
promote() {
sourced="$1"; shift
. "$sourced"
env - \
"HOME=$HOME" \
sh -c ". $sourced; env" | cut -d= -f1 | while read -r var; do
val="$(eval "echo \"\$$var\"")"
tmux set-environment -gt local "$var" "$val"
done
}
What's happening here is we're sourcing our file from within a shell with an empty environment (apart from the HOME we add), and print out our new env vars. We pipe those into a cut to extract the variable of each line, storing it in a variable called var. After some meta magic with eval to get the indirect value of that variable from the current shell, we update our tmux target session. In this case, local is the name of our tmux session.
After wrestling with different solutions, I came up with this bash function added to my .bashrc file:
if [[ -n $TMUX ]]; then
_fix_ssh_agent_in_tmux () { if [[ ! -S $SSH_AUTH_SOCK ]]; then eval export $(tmux show-env | grep SSH_AUTH_SOCK); fi }
ssh () { _fix_ssh_agent_in_tmux; command ssh $#; }
scp () { _fix_ssh_agent_in_tmux; command scp $#; }
rsync () { _fix_ssh_agent_in_tmux; command rsync $#; }
fi
If the shell is running within tmux, it redefines 'ssh' to a bash function that tests and fixes SSH_AUTH_SOCK before actually running the real ssh command.
Note that tmux show-env -g also returns a value for SSH_AUTH_SOCK but that one is stale, I assume it's from whenever the tmux server started. The command above queries the current tmux session' environment which seems to be correct.
I'm using tmux 2.6 (ships with with Ubuntu 18.04) and it seems to work well.