Tmux – Why Tmux Sets TERM Variable to Screen

I guess you could run your full-screen program in tmux or Screen pane directly, without additional shell session (shell is just another program).

Another way, which I prefer, is to use tiling/stacking window manager like i3 and terminal program urxvt. The latter has very fast daemon/client structure, which allows opening new windows instantly, so you could run any program in new window this way:

urxvtc -e <command> <args>

This needs to be in a script or a function, really.

New window will take one half, one third, or so on of the screen in default tiling mode. Combined modes are also possible in these WMs.

There is some information on 256-color support in the tmux FAQ.

Detecting the number of colors that the terminal supports is unfortunately not straightforward, for historical reasons. See Checking how many colors my terminal emulator supports for an explanation. This means that

• tmux cannot reliably determine whether the terminal supports more than 8 colors;
• tmux cannot reliably communicate to the application that it supports more than 8 colors.

When you're in tmux, the terminal you're interacting with is tmux. It doesn't support all of xterm's control sequences. In particular, it doesn't support the OSC 4 ; … control sequence to query or set color values. You need to use that while directly running in xterm, outside tmux.

If you run tmux -2, then tmux starts with 256-color support, even if it doesn't think that your terminal supports 256 colors (which is pretty common).

By default, tmux advertises itself as screen without 256-color support. You can change the value of TERM in .tmux.conf to indicate 256-color support:

set -g default-terminal "screen-256color"

You can use TERM=xterm-256color or TERM=screen-256color on Ubuntu. These values will only cause trouble if you log in to a remote machine that doesn't have a termcap/terminfo entry for these names. You can copy the entries to your home directory on the remote machine; this works with most modern terminfo implementations.

# From the Ubuntu machine to a machine that doesn't have *-256color terminfo entries
ssh somewhere.example.com mkdir -p .terminfo/s .terminfo/x
scp -p /lib/terminfo/s/screen-256color somewhere.example.com:.terminfo/s/
scp -p /lib/terminfo/x/xterm-256color somewhere.example.com:.terminfo/x/