tmux

I have started to experiment with using tmux recently. It is a terminal multiplexer, sort of like a tiling window manager / tab bar that runs purely in the terminal. It has decent mouse support, so it is not that different than using a GUI terminal with tabs, plus panes. And it works and gives me roughly the same config and interface across platforms and terminal apps, including pure terminals like kmscon and potentially on remote servers. I have been moving toward a lighter weight, simpler, more terminal heavy, dotfiles friendly setup, and this fits into that. I spent entirely too much time getting my tmux configuration to my liking.

I had played with screen, an older alternative, a little in the past. I like that screen is installed by default on Macs and most Linux distros, but it isn't as easy to work with or configure nicely, especially the quite old version that Macs have. I will most likely just use screen on remote servers where I don't want to (or can't) install extra software, but for local use I may try using tmux for managing my terminals instead of GUI tabs going forward.

Install

tmux is in package managers for most distros and Termux, and homebrew for Mac, as "tmux". It can be installed with one of:

brew install tmux
sudo apt install tmux
sudo dnf install tmux
pkg install tmux

or whatever package manager the OS has.

Config

Most of the default interaction with tmux (as well as screen) are done by key bindings that involve hitting a key combo called the prefix, followed by another key. By default, the prefix is Control-b. That's a little hard to press, so most people change this. I made two, one on each side of the keyboard. I used control keys that I don't use that often for their normal terminal functions, because tmux overrides this and they have to be pressed twice to send the key as normal to the terminal. My config for this looks, in ~/.config/tmux/tmux.conf, is like:

set -g prefix C-f
bind C-f send-prefix
set -g prefix2 C-l
bind C-l send-prefix -2

To see the keys available to use, look at the man page (man tmux) or run tmux list-keys -N (the -N option improves the format and shows only the normal keybindings).

Since vim is my preferred editor, I had to turn on the vim mode keys with:

set -g mode-keys vi

This only affects copy mode and command mode, but is still nice. Though it benefits from a few additional key bindings:

bind -T copy-mode-vi v send -X begin-selection
bind -T copy-mode-vi y send -X copy-pipe

Speaking of copy, to copy to the OS clipboard:

set -s set-clipboard external

To help ensure the proper clipboard is used for copy-pipe, I run an external script with something like:

run-shell -E '. ${DOTFILES:-~/.dotfiles}/sh/env.sh && tmux set -g copy-command "$(getcopy)"'

The loading of my dotfiles environment and passing through a shell is done because tmux doesn't necessarily make the environment available in the config, especially if loading tmux directly in a terminal rather than starting it from a shell. I want the $PATH to have the folder where getcopy is. That getcopy script looks something like:

#!/bin/sh
if [ "$(uname)" = 'Darwin' ]; then
	echo 'pbcopy'
elif [ -n "$XDG_CURRENT_DESKTOP" ]; then
	if command -v 'wl-copy' > /dev/null; then
		echo 'wl-copy'
	elif command -v 'xsel' > /dev/null; then
		echo 'xsel -i'
	elif command -v 'xclip' > /dev/null; then
		echo 'xclip -selection clipboard -i'
	fi
fi

though that hasn't been thoroughly tested in varying situations.

On copy mode, it normally copies when releasing the mouse on a drag. I find this difficult to use, so I disable that with:

unbind -T copy-mode-vi MouseDragEnd1Pane

I set the base indexes at 1 to make switching windows and panes via keyboard commands easier, like:

set -g base-index 1
setw -g pane-base-index 1

I also have altered the default appearance quite a bit. Moving the status bar to the top is done with:

set -g status-position top

Color / style is done with a bg=green,fg=black type setup, which can also have comma separated attributes added, like bold or italics. These can be set on any -style settings directly, or as part of -format settings by putting them in an escape #[] block, which changes the style for following text. I wanted to set my colors differently depending on if the terminal supported 256 colors or not, so I used variables, which were a little difficult to use. On settings with variables, I had to use set -gF instead of set -g, which also required putting ## for any escapes that need to be dynamic. My color conf looks something like:

%if "#{>=,e|#{$TJMTCOLORS},256}"
	set -g @c1Alt "black"
	set -g @c1 "green"
	set -g @c1Emph "colour47"
%else
	set -g @c1Alt "black"
	set -g @c1 "green"
	set -g @c1Emph "brightgreen"
%endif

That $TJMTCOLORS is an environment variable set to tput colors in my env.sh. The custom "options" must all be @ prefixed.

Then some examples using them look like:

set -gF status-style "bg=##{?client_prefix,#{@c1Emph},#{@c1}},fg=#{@c1Alt}"
set -gF window-style "bg=#{@c0DimAlt},fg=#{@c0Dim}"
set -gF window-active-style "bg=#{@c0Alt},fg=#{@c0}"

My other settings and full config can be found in my dotfiles. The man page is pretty good at describing most things about the config options.

With all this use of the control key, I decided to finally switch my caps lock key to work as control. For Mac, go to "System Settings > Keyboard > Keyboard Shortcuts… > Modifier Keys" and set "Caps Lock key" to "^ Control". For kmscon, put xkb-options=ctrl:nocapsin /etc/kmscon/kmscon.conf.

Also of note, many modern terminals automatically handle scrolling in alt screens like less. When I enabled tmux, this stopped working. I had to set my --mouse in my LESS environment variable, eg LESS="--mouse" to get its own mouse capability working. This isn't nearly as smooth or as smart as the terminal's though.

So far

I have switched some of my terminals to open with tmux directly instead of a normal shell. I'm still getting used to the setup and remembering which keys to use for that versus vim, the surrounding GUI (if applicable), etc. I like how the mouse works with tmux itself, switching panes and windows (working like tabs) and, with the pane border enabled, there are even buttons to zoom / unzoom and close panes.

I may see if there's more I can do with the mouse and with other bindings to make my usage easier. I will probably tweak my color scheme, as the top bars might be a bit bright. Also, I have some stuff set to bold, which in kmscon and some other terminals, is handled as bright instead. brightblack is much different than black. Will probably want to handle that differently.

My biggest disappointment so far is with the scrolling, especially of alt screens. It isn't as smooth or nice as the capable GUI terminal apps' own abilities, even with --mouse enabled for less. And for ssh I'd have to do the same thing for each remote. That can also send a lot more traffic over the network from what I've read.

I also have had problems with selecting text with the mouse. The copy mode won't work directly with a mouse drag in less with mouse mode enabled, for instance. On Mac, I can use fn+drag to grab text with the terminal's own selection, but that takes more effort than just dragging.

So for now I'm just using tmux in some places to get a feel for if the advantages outweigh the (mostly mouse related) disadvantages.