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Comment by rogerbinns | Hacker News Reader

The single most irritating thing about tmux is that viewers have to look at the same window or whatever it is called. My typical usage pattern is to connect twice, have one window where there is a long running task I want to monitor and a second where I am typing commands. But I can't show one in one connection and the other in the other connection.

Note that I use byobu to front end things, and when using screen this can easily be done. I have seen workarounds that involve using multiple copies of tmux talking to each other in various heroic configurations but that is silly.

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I believe tmux 1.8 supports this use case.

From the manpage (for new-session): If -t is given, the new session is grouped with target-session. This means they share the same set of windows - all windows from target-session are linked to the new session and any subsequent new windows or windows being closed are applied to both sessions. The current and previous window and any session options remain independent and either session may be killed without affecting the other.

I've started running tmux in all my terminals automatically, and conveniently sharing a "master" session between them all.

Instead of running tmux directly, I have a small script which creates a session named TMUX-MASTER if it doesn't already exist, and immediately detaches it. All the clients that I actually interact with are created separately and automatically grouped with the TMUX-MASTER session.

To prevent my system from being clogged by dozens of detached client sessions, I rebound prefix+d to kill-session, killing the client session but leaving my TMUX-MASTER session untouched. Closing terminals while running these client sessions, however, still leaves my system cluttered with dormant client sessions.

I'd like to see if a "ephemeral" option (it'd need a better name) could easily be added to new-session, which would cause the created session to just die when it's told to detach, or receives the HUP signal. It'd simplify things a bit.

I always have two copies of tmux running, for this very reason. Someone out there surely must have a better solution.

I used to do this all of the time in screen, but I haven't done so since switching to tmux (haven't run upon the situation). You've inspired me to look into it.

First, terminology. I know that tmux has: servers, clients, windows, sessions, and panes, but I've never bothered to understand how they fit together.

* server - The server is a process that listens on a unix socket, and accepts connections from clients. Each server manages one or more sessions, which is a grouping of windows.

* client - A terminal connected to the server. Each client connects to a single session on the server.

* session - A collection of windows on a server.

Each session has a single 'active window.' When you connect two clients to a single session, switching the current active window affects what both clients see.

Solution:

Windows can be shared between sessions, and a single window can be present in multiple sessions. This culminates in a tmux feature called "grouped sessions" where multiple sessions are linked and share the same windows. You can use this command:

  tmux new-session -t session-id

source: http://unix.stackexchange.com/questions/24274/attach-to-diff...

This is so much more complicated! When using byobu I use F3 and F4 to cycle to previous and next window. I can't understand why they think that by default I want all of the viewers to switch at once.

Having the viewers switch by default is useful for demos, when you are showing something to someone. And it's the simplest behaviour for their data structure. So I can see some logic to why they designed it that way.

I'm glad you raised this issue because I've only recently moved to tmux and would have been stung by it.

Could you abstract it away behind a shell alias? I used this:

   alias tmuxc='tmux new-session -t 0'

I don't know since I am using byobu to front end all this, and it is what runs tmux/screen under the hood in the end.

I think that the main issue that you're having is that 'active window' is an attribute of a session, and not of the client. If 'active window' were specific to a client, then two clients could switch windows independently while connected to the same session.

You could petition for an option to the `attach-session` command that automatically creates a new session grouped to the session that you're 'attaching' to. IIRC, you can't attach two 'clients' to the same (GNU) screen session unless you use the -x option, so it's not like it's the 'default' behaviour for screen either.

Edit:

I wasn't thinking, but `new-session` will automatically connect to the new session you created, so there is no need for an option to `attach-session`. So when you want to connect a second client, just:

  # find the session you want
  $ tmux list-sessions

  # create a grouped session
  $ tmux new-session -t SESSION_ID

Edit 2:

  | This is so much more complicated!

Depends. If you're using byobu, then you're already attempting to abstract away a bunch of the complexity of GNU screen, so it's not like you would find less complexity if you dove into the screen internals. It's also this design that makes it easier to do complex things that screen can't do with its windows.

  | When using byobu I use F3 and F4 to cycle to
  | previous and next window.

Maybe you're misunderstanding. You still use the same tmux bindings to switch windows, it's just the setting up of the session that requires slightly more work when connecting a second client.

Since I use byobu I neither know nor care what is going on under the hood. I use 4 keystrokes - F2 to start a new shell, F3 to cycle back, F4 to cycle forwards and ctrl-F5 to reconnect sockets (GPG agent, DBUS etc).

I did switch it from screen to tmux because tmux definitely works better for other things and seems more responsive when there is lots of output. By default screen did let each client view independent of any other.

I don't see how to automate getting the behaviour I want (independent client views) as typing commands and feeding them into tmux would be a huge pain (especially as byobu is already doing that).

It really depends on what your workflow is. If you only ever have a single tmux session, then you could write a quick script that starts a session if it doesn't exist, but if it does, automatically creates a mirrored session and connects to it. In this workflow, you can assume which session you want to group with, but if you work with multiple sessions, then there is no way to automatically do this. E.g., you could run something like:

  $ tmux.sh session-name

which would create the session the first time, and create a grouped session, the second time.

Edit:

I've created a little script for this: https://github.com/bsandrow/tmux.sh

I created a byobu ticket to cover this issue as it is what ultimately starts/connects tmux pointing to this thread. Thanks for the solution. https://bugs.launchpad.net/byobu/+bug/1168734

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