Category: tmux

How to resize tmux windows using OS X terminal

A while back I pointed out a blog post by someone else, which described how to get C-left and C-right working in tmux and OS X. Now I noticed that I cannot resize windows in tmux. This is because tmux seems to expect xterm keys for C-arrow. The xterm keycodes for the arrow keys are:

  • left key: ^[[D
  • right key: ^[[C
  • up key: ^[[A
  • down key: ^[[B
  • C-left: ^[[1;5D
  • C-right: ^[[1;5C
  • C-up: ^[[1;5A
  • C-down: ^[[1;5B

I can now configure OS X terminal to send those key codes, and tmux works fine. However, other apps running in tmux will break, because they don’t expect to get xterm key codes. I found a workaround in the ArchWiki, which suggests to create your own terminfo entry. I will try that and report back here.

Update: The solution is adding two lines to the ~/.tmux.conf file:

set -g default-terminal “xterm-256color”
setw -g xterm-keys on                   
Update 2: And here is my OS X Terminal.app configuration:

Update 3: And a very last update… It seems that tmux does not support bce (background color erase), which xterm does. This is a problem for progams like htop, vim, or mc. You will see rendering errors, if you do not fix this.

So you need to make your own terminfo file and own terminal type, called xterm-256color-nobce. You can do this on the command line:

pi@raspberrypi ~ $ infocmp xterm-256color | sed ‘s/bce, //’ | sed ‘s/xterm-256color/xterm-256color-bce/g’ > xterm-256color-nobce

This will create a new terminfo source file, which does not advertise the bce feature. You can install this with the following command:

pi@raspberrypi ~ $ sudo tic ./xterm-256color-nobce

This makes the terminal type xterm-256color-nobce available. After this, change your ~/.tmux.conf once again, to use the new terminal type per default:

set -g default-terminal “xterm-256color-nobce”

Update 4: To make the Ctrl+Arrow keys also work in regular OS X Terminal, you need to edit or create ~/.inputrc to contain this:

# xterm keys for skipping a word
“e[1;5C”: forward-word
“e[1;5D”: backward-word
“e[5C”: forward-word
“e[5D”: backward-word

The “1;” variant is otherwise not recognized by GNU readline on OS X.

How to run tmux via ssh instantly

With my Raspberry Pi, what I do very, very often is this:

localhost$ ssh raspberrypi.local    # Here I already type the next command and wait a while
raspberrypi$ tmux attach

This is all well and good, but sometimes the Pi is down, and I will attach to one of my local tmux sessions. Very annoying. Instead you could try to do this:

localhost$ ssh raspberrypi.local tmux attach
not a terminal

Well, that did no good. So a look at the man-page of ssh or a quick search reveals this gem:

localhost$ ssh raspberrypi.local -t tmux attach

This allocates a pseudo terminal, which is needed by tmux to function correctly. This is also done by ssh, if no command is given, but a login shell is spawned.

Some tmux cheats

There’s a lot of stuff you can do with tmux. Here are some nice to know things:

  • C-b C-o: cycle contents of current windows (or swap if there are only two windows)
  • C-b C-SPC: switch between vertical and horizontal split
  • C-b n, p: next or previous screen
  • C-b [: copy mode
    • Use Emacs bindings to copy and paste:
    • C-SPC: begin selection
    • C-w or M-w to copy
  • C-b ] to yank (paste)

    How to get Ctrl+Arrow working for programs running in tmux?

    The key combination of Ctrl+arrow key is often used for skipping forward or backward whole words. This can be used in the bash command line, Emacs and many other programs. However, when I am using tmux, this will not work. You can fix this, by adding the following to your ~/.tmux.conf:

    set-window-option -g xterm-keys on
    This was explained in a nice superuser Q&A.
    You can interactively try out tmux commands by hitting C-b : — this will enter the command mode. You can use tab to complete commands.