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Comment by metafunctor | Hacker News Reader

This is something to watch out for especially if you're switching from screen to tmux.

When you start a screen session, it will always copy the environment from your shell. When you start a second screen session, it will inherit a possibly different environment.

But tmux, on the other hand, spawns a tmux server when you first start a session. It'll copy the environment from your shell. However, from that point onwards, new sessions will use the environment from the server and will not copy the environment from your shell.

I like screen's behavior more. A frequent use case is to start a long-running command as a sort of ad-hoc background job. That's really easy with screen (just run screen and run your command, it will always use the parent shell's environment) but relatively easy to screw up with the environment when done with tmux. It kind of works only if you don't have a tmux server already running.

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I have tried on multiple occasions to migrate to tmux (because gestures vaguely "it's the future", screen's codebase is ancient and can still connect directly to a serial port etc), but I just don't like the primitives that tmux gives you ((servers,) sessions, windows, panes).

I use a nested setup with screen where each level of nesting has a different escape key, this works really well when I want an inner screen to be on a different machine.

  screen '-e^Zz' -S meta

and then inside that one

  screen '-e^Oo' -S project1

and for a session on a remote machine

  mosh some_server -- screen '-e^Oo' -S remote_session_name

I haven't figured out a way to get this to work well with tmux, because the local tmux server doesn't know about the remote tmux sessions. Whereas with screen, screen doesn't need to know or care about that.

(edit: I use shell aliases, I don't type out the '-e^Oo' etc every time)

I use backtick, hen two back ticks, then four. Only rarely have to go to eight backticks. :)

> screen's codebase is ancient and can still connect directly to a serial port

That particular feature is pretty important to me, and it would suck if it got removed. Just because a codebase is ancient doesn't mean it's useless.

Embedded Linux user? We used screen & minicom extensively in my unis satellite lab

i do exactly that with tmux. the primary difference is that don't nest tmux locally, but each tmux session is on a different computer, so they all just need their local config where the escape key is specific to the computer.

why does the local tmux server need to know about the remote tmux session?

I can't figure out an use case for your setup, can you help a bro out?

Nested sessions. Hypothetical:

  local computer with screen
  \
   \ ssh/mosh to remote A, run screen
    \
     \ ssh/mosh to remote B, run screen

If each uses the same prefix (the default is C-a for screen, C-b for tmux) then you have to send it multiple times to send a command to the screen sessions on either of the remote systems. If you give each a unique prefix then you can send the prefix once and it goes directly to the desired screen session.

Easier to give each system its own prefix that's constant regardless of depth, though, than trying to remember "Did I connect to A first or B first today?". Or, better in my experience, don't nest them. It's a pain however you choose to deal with the prefix problem.

Instead of keeping N terminals open for N projects, I usually keep only one open and put each project in a screen session, then wrap them all in a “meta” session.

I started using this pattern before I moved to macos, but now that I’m usually on a mac, it helps because I still haven’t gotten used to macos window / desktop management. Managing one terminal is easier than a half dozen.

I do that except with terminal emulator sessions. One window with few tabs per virtual desktop, as I rarely need to have more than 2-3 projects open at the time it works fine.

But... isn't tmux sessions exactly what you'd need for that? One session per project, then just connect to servers from within tmux windows

There is even switch-tree (default C-b w) that will show each session with every sub-window in it, and even preview window below that showing each terminal (refreshable via space)

I'm looking to skip tmux and migrate straight from screen to zellij instead, since it's also modern. I don't have many problems with screen, but lack of full color support (for vim) and wanting more terminal control codes (hyperlinks, text underlines, sixel, etc) speak in favour of using a more modern solution.

Thanks for pointing out zellij [0]. I wasn't aware of it and am really glad to have read about it.

It's odd. A couple of days ago I watched Tristam Oaten's No Boilerplate video "Oxidise Your Life" [1] and it left me thinking about how Rust is moving some programmers to rewrite tools in Rust and, while at it, adding modern features. It's nice to see that.

[0] https://zellij.dev/screencasts/

[1] https://www.youtube.com/watch?v=dFkGNe4oaKk

I want to love zellij but can't get over how it binds its own actions to practically every key (vs screen/tmux which take just one, the prefix). Do people who use it not use any programs that use control or alt keys?

I also trying to come to terms with this, mostly need to design new custom key settings.

Zellij has Lock interface, default Ctrl+G, which you can use and in that mode it only takes that one key, but it's a bit different from how screen works.

Yeah, but that's more than twice as many keypresses now.

I recommend using tmux mode and adding its keybind to locked mode, that way you get the same key interactions as tmux itself. Sadly, zellij doesn't offer the same options for which key that will be (in screen and tmux I like using C-] cause it's usually unused, but you can't use that one in zellij)

This can be changed: I use zellij and just rewrote its config file to place almost all the keys in a single mode, basically 1-1 with tmux.

That said, I must admit that zellij doesn't add a whole lot to my workflow relative to tmux. I think I'm just easily distracted by the new-and-shiny.

> screen to zellij instead

FFS. Can't we, at some point, be done with wheel re-invention?

Wait until you find out how many people in the 21st century are still iterating on the idea of the wheel itself. Imagine if nobody tried reinventing wheels since they were first introduced and you have your answer.

> Can't we, at some point, be done with wheel re-invention?

You do realize how much of technology and coding is literally re-writing things constantly until they work for [insert stakeholder here]. Right?

I was quite satisfied with tmux but this issue (and one other) really drove me to seek an alternative like zellij so bad, but just couldn't settle on it for one reason or another. Instead I ultimately found refuge in kitty term which as a whole emulator is an overkill, but it's a great replacement and mostly as customizable. It does a good job with windowing - I particularly like the xmonad style window size switching. But there are still some parts of the tmux ecosystem I miss, like tmuxinator and the extracto plugin but otherwise most of my needs have been met, and the speed is a welcome bonus. So, can definitely recommend kitty as a good tmux alternative.

I just have one level and search function.

C-b s gets me graphical(via rofi + some scripting) searchable list of windows, in rare cases where I'd need tens of them.

But it took me a while to make tmux keybindings that are fast & convenient, screen defaults (aside from C-a that collides with bash/emacs) on keybindings are way better.

> I haven't figured out a way to get this to work well with tmux, because the local tmux server doesn't know about the remote tmux sessions. Whereas with screen, screen doesn't need to know or care about that.

I'm missing something here. Why does tmux need to know or care?

I occasionally open tmux on a remote machine from within a local tmux.

Using c-bb to get to the nested one doesn't seem that bad to me as long as it's only 2-deep.

But why not just change the escape key on each machine's .tmux.conf?

The problem here is the reliance upon environment variables being set by parent processes. That's always felt weird to me.

I think tmux's choice is actually the sane one. You create the server once, then there's no more question about what environment variables are going to be established in the future.

When you create a new tmux window, you should know if there's already a server spawned.

It would make sense if there were 2 commands, tmux-server for starting the server and tmux-client for starting the client. The client would then support options to connect to an existing server or spawn a new one.

I'm a big fan of abstracting away details of little importance. But if I risk using an old server with stale values in its environment, I prefer that to be made explicit and not abstracted away.

I agree that it is more sane and predictable.

I'm pretty happy with this behaviour and being able to tweak it if I need more.

How is that "predictable"? The standard behavior for more or less everything is that, by default, when you run a process, it will get its environment from the parent process. Getting its environment from a magical hidden server process that a casual user may not even know about is the opposite of "predictable".

it's not magical or hidden. every invocation of tmux is a call to a running tmux server. the only exception is when no server is running, in which case a new one is started.

i have tmux running all the time. started once when i connect to a server for the first time, it keeps running until the server is rebooted. i have tmux sessions that go back years.

the only time the environment is causing me trouble is when a new ssh connection is forwarding an ssh agent, which doesn't get transferred into the tmux session when i attach. but screen would not help here either. if you connect to an existing screen session it has the same problem. we really want a way to adjust the environment for specific variables on attach.

If you run an SSH client process to connect to an SSH server, the resulting SSH session will not inherit the environment from the parent process of the client by default. Although not the same, connecting to a tmux server is more similar to that than starting a regular child shell.

> ...the reliance upon environment variables being set by parent processes. That's always felt weird to me.

I don't really agree. When I start a program in a shell, I expect it to inherit the environment of that shell. That's just how things have always worked, modulo some special cases (sudo, running a new instance of the shell in login mode, whatever).

I personally don't think that's weird, but even if I did, what I care most about software behavior is predictability. Software should do what is expected and common, and if it does not, it should have a very good reason, and should find a way to make that obvious to the user every time it does it.

This is just bad UX on tmux's part.

> When you create a new tmux window, you should know if there's already a server spawned.

What? Why? I use screen on and off, not super often. When I start a screen instance, I don't always know or care if I have another instance running somewhere. And yes, because screen follows what I'd consider a more predictable model here, I end up with the environment variables I expect.

I think whenever we attack a UX problem by saying "the user should know X", we've already lost. You can't assume that you know how the user is going to use your software, or what their state of mind will be when starting it. That's just silly.

> When I start a program in a shell, I expect it to inherit the environment of that shell.

That's exactly how tmux works. You start a server, it inherits the environment of the current shell. You create a new session in that server, it inherits the environment of the server.

I don't understand how forcing tmux to re-load the current local environment for each new shell is saner behavior. One natural consequence would be that new panes in existing sessions are also created with the new env vars, which is obviously undesirable.

>> When I start a program in a shell, I expect it to inherit the environment of that shell.

> That's exactly how tmux works. You start a server, it inherits the environment of the current shell. You create a new session in that server, it inherits the environment of the server.

Whether that makes sense depends on if your mental model has starting a server and connecting to a server to create a new shell as distinct actions, as opposed to a singular action of connecting to a conceptually always-present persistent environment and starting a shell there. Admittedly tmux’s interface is mostly organized along the former lines, but given I prefer `tmux new -A`, my own model seems to follow the latter.

I don't know about other people - but I spend greater than 99.9% of my time inside a tmux session. It is my windowing environment. I was reading the original post and just kept furrowing my brows wondering "Under what possible scenario could any of this possibly be a problem?"

It's kind of interesting reading through the threads here and seeing how people don't spend their time inside tmux all the time but instead "start an instance on demand" - which I've never done but I guess works for some people's workflow?

I'm genuinely crippled trying to use a terminal without tmux after having used it for so long - don't have the faintest clue how to copy/paste/search/organize windows without it.

I want to echo this sentiment as well. I never use bare terminal sessions. Not locally, and especially not remotely.

I think the tmux sentiment in question is held by people new to the tool or that don't use it as a normal part of their workflow or day-to-day.

Something like yakuake does tabbing, splitting, and is scriptable via dbus commands. There is no strong need to learn tmux key bindings to use locally.

I was a casual tmux user until I got stuck in a portable trailer in Dubai working for DEWA on their grid, and they had us using a janky remote terminal Remote Desktop setup that didn't have any form of mouse pass through to the linux terminals we were doing work on. So - copy/paste were not possible which made work a pain. I gave them a DVD (!) containing the various ncurses/libevent/tmux code - and voila - I finally had a working environment.

I spent 2+ months in that trailer for 6-8 hours/day - and tmux became so embedded in my finger DNA, I never looked back.

I routinely bounce between WSL, Linux, and MacOS and never have to remember any of the keyboard shortcuts for the terminal programs, or whether it's been installed, and my fingers never leave the keyboard - and I can almost always outperform someone trying to select/copy with a mouse/touch pad. My .tmux.conf is the only thing I pull along with me.

Also - just thinking about it - tmux is more than just a windowing environment - it also does project management. I have a workflow where every new project/issue/incident gets its own named window - and then I break up that window into a set of 4-8 panes based on systems (or sets of systems) I'll be working on. They all share the same bash_history. As I get hit with interrupts, I bounce between sessions and when I come back - my whole thought process/work history is back in that named window with panes. It's not unusual for me to have 45-50 open panes at a time - all perfectly organized by project/named window. With the resurrect plugin, and intelligent use of my bash config - I can (and do) pull everything (scroll back history, bash history, etc..) onto another system if needed (great if you need to recreate your work history and you no longer have access to the original terminal environment).

As I close off/complete projects, I terminate the window - but the bash history is kept clean in ~/.tmux/bash_history/window_name in case I ever need to start working on it again (recreating the window with the same name pulls back in the bash history)

Introspecting here a little, this honestly is probably more a function of me spending 40+ hours in a terminal environment than anything a rationale casual user would ever want to do.

Ha! I didn't see you response before writing mine, but, yeah, I had the exact same reaction!

If I'm running in a GUI terminal I can do most of those in there instead. I mostly end up using tmux if I need multiple tabs inside a ssh session.

Right but then when you ssh to your existing computer from another you won't have all your windows!

Sure, if this is a big part of your workflow then that makes sense. Personally, I end up running 1-2 workstation machines with GUIs that I sometimes remote out from, but ~never into (apart from sometimes retrieving files from the desktop when I'm away).

You are not using tmux for what it's designed to be used. It's not for running long-running processes, even though you might use it this way (you could also use eg. Photoshop to run long-running processes, after all, it has an embedded JavaScript interpreter with some extra functionality that might allow you to do that).

tmux serves the same purpose as DE, except w/o the whole windowing system etc. It's to allow you to switch between multiple applications which require terminal for interaction.

I spend close to 100% of my time at work inside tmux, and I never needed to answer a question "where do the process variables come from?" -- it's irrelevant in the same way how you don't ask where does Gnome get its environment variables from. You simply don't rely on environmental variables when running tmux / don't care about them.

I disagree. tmux default behaviour suits my workflow much better. It's complex enough problem that there is no perfect default so complaining this or that doesn't fit you when you can just change it so it does is pointless.

Environment variables get immutably set when you run the process, that screen would re-evaluate them when launching another window is bizarre. I'd expect the opposite case to be a problem, that when using screen you'd export environment variables by accident more often.

FWIW, as someone who uses screen, to me the opposite is "bizarre"? ;P I am at a shell, and I run "bash". This opens a new shell, but inherits both the environment and the working directory from my shell. Or maybe I run "ls": same thing. Now I run "screen bash" or "screen ls"... this should intuitively run the command as if I had just run the command but do so in a new "window". It would be absolutely ridiculous if "screen ls" didn't inherit the environment from the current shell.

Looks like zellij follows the same behavior as screen, if I'm testing right. I also prefer screen/zellij's choice here.

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