Switching from GNU Screen to tmux

GNU Screen is a fantastic program. It is, however, more or less abandoned. tmux promises to be a more full-featured alternative, with cleaner source code and easier configuration. This is the .tmux.conf file I'm currently using.

# change tmux key-bindings to screen key-bindings (with ^O as prefix)

# Set the prefix to ^O
unbind C-b
set -g prefix ^O
bind a send-prefix

# Bind appropriate commands similar to screen.
# lockscreen ^X x 
unbind ^X
bind ^X lock-server
unbind x
bind x lock-server

# screen ^C c 
unbind ^C
bind ^C new-window
unbind c
bind c new-window

# detach ^D d
unbind ^D
bind ^D detach

# displays * 
unbind *
bind * list-clients

# next ^@ ^N sp n 
unbind ^@
bind ^@ next-window
unbind ^N
bind ^N next-window
unbind " "
bind " " next-window
unbind n
bind n next-window

# title A
unbind A
bind A command-prompt "rename-window %%"

# other ^O
unbind ^A
bind ^O last-window

# prev ^H ^P p ^? 
unbind ^H
bind ^H previous-window
unbind ^P
bind ^P previous-window
unbind p
bind p previous-window
unbind BSpace
bind BSpace previous-window

# windows ^W w 
unbind ^W
bind ^W list-windows
unbind w
bind w list-windows

# quit \ 
#unbind \
#bind \ confirm-before "kill-server"

# kill K k 
unbind K
bind K confirm-before "kill-window"
unbind k
bind k confirm-before "kill-window"

# redisplay ^L l 
unbind ^L
bind ^L refresh-client
unbind l
bind l refresh-client

# split -v |
unbind |
bind | split-window

# :kB: focus up
unbind Tab
bind Tab select-pane -t:.+
unbind BTab
bind BTab select-pane -t:.-

# " windowlist -b
unbind '"'
bind '"' choose-window

# Q break-pane (close all other panes)
unbind !
bind Q break-pane

#####################################################################

# enable 256 color support
set -g default-terminal "screen-256color"

# make prefix+S toggle status line visibility
bind S set -g status

# more or less screen style split
# prefix+H: split horizontally by grabbing the previous window into the new pane
# prefix+V: split vertically by grabbing the previous window into the new pane
bind H join-pane -ht :-1
bind V join-pane -vt :-1

The bulk of the code is for making tmux key-bindings like those of GNU Screen (up until the seprator line). Most of that code is copied from the sample config file that came with the Arch package (in /usr/share/tmux/screen-keys.conf). The rest adds these functionalities:

• Enable 256 color support.
• Add a key-binding for toggling status line visibility.
• Add a pair of key-bindings for screen style splitting. In screen, when you split a window, two windows are created and each can be rotated so that it contains one of the previously created windows. In tmux, splitting results in creating two "panes". A window can contain several panes. This is usually desirable (with this config, accessible through the use of prefix+| and prefix+% shortcuts). However, sometimes you might want to split the window so that the new pane contains one of the previously created windows. The last two lines add the prefix+H and prefix+V key-bindings that make this possible (one for splitting vertically, the other horizontally). The new pane will contain the window before the current one.

I also added this to my .stumpwmrc to make switchig to the emacs inside tmux easier (again, this is not exactly correct, but it works most of the time for me).

(defcommand emacs-in-tmux () ()                                                                                                                                                                
  "attempts to switch to an emacs instance run in a tmux window                                                                                                                          
called 'emacs', itself inside a urxvt instance."                                                                                                                                               
  (let ((ret                                                                                                                                                                                   
         (run-shell-command "tmux select-window -t emacs ; echo $?" t)))                                                                                                                       
    (if (eql (elt ret 0) #\0)                                                                                                                                                                  
        (run-or-raise "urxvt" '(:class "URxvt"))                                                                                                                                               
        (message "no screen session found."))))                                                                                                                                                
(define-key *root-map* (kbd "C-e") "emacs-in-tmux")

My GNU Screen Configuration

First an update on my latest setup. I switched to Arch Linux a while back and I'm rather happy with it so I'm not thinking of going back to Ubuntu at the moment despite the fact that I'm hearing it's in a good condition.

Second I've started using screen a lot more than before. Specifically, I began running my emacs session inside screen a while back, so that I can connect to my home computer from other places and attach to my screen session and use the running emacs instance. More recently, I've switched to using tmux instead of screen but for the sake of keeping history, I'm posting the code and configuration I used to use here. tmux will be the subject of another post.

This is the .screenrc I used:

escape ^Oo                                                                                                                                                                                     
vbell off                                                                                                                                                                                      
                                                                                                                                                                                               
# Scrollback buffer size in lines                                                                                                                                                              
defscrollback 5000                                                                                                                                                                             
                                                                                                                                                                                               
startup_message off                                                                                                                                                                            
                                                                                                                                                                                               
hardstatus alwayslastline                                                                                                                                                                      
hardstatus string '%{= kG}[ %{G}%H %{g}][%= %{=kw}%?%-Lw%?%{r}(%{W}%n*%f%t%?(%u)%?%{r})%{w}%?%+Lw%?%?%= %{g}][%{B}%Y-%m-%d %{W}%c %{g}]'                                                       
                                                                                                                                                                                               
# enable support for 256 colors                                                                                                                                                                
term screen-256color                                                                                                                                                                           
terminfo rxvt-unicode 'Co#256:AB=\E[48;5;%dm:AF=\E[38;5;%dm'                                                                                                                                   
                                                                                                                                                                                               
# fix for residual editor text. sometimes when you run an editor and                                                                                                                           
# close it, some of its text may stay visible. this fixes that                                                                                                                                 
# problem.                                                                                                                                                                                     
altscreen on                                                                                                                                                                                   
                                                                                                                                                                                               
screen -t  emacs       0        emacs -nw                                                                                                                                                      
screen -t  shell0

It changes the screen prefix to ^O so that it doesn't clash with the emacs shortcut. It turns off the visual bell, enlarges to scrollback buffer, turns off the welcome screen, adds a status line, enables 256 color support inside screen, enables alternate screen (so that residual text from some editors will not stay visible after closing them), and finally starts a shell and an emacs instance.

I also added this code to my .stumpwmrc so that I can switch to emacs in the usual way (by pressing C-t C-e):

(defcommand emacs-in-screen () ()                                                                                                                                                              
  "attempts to switch to an emacs instance run in a gnu screen window                                                                                                                          
called 'emacs', itself inside a urxvt instance."                                                                                                                                               
  (let ((ret                                                                                                                                                                                   
         (run-shell-command "screen -X select emacs > /dev/null ; echo $?" t)))                                                                                                                
    (if (eql (elt ret 0) #\0)                                                                                                                                                                  
        (run-or-raise "urxvt" '(:class "URxvt"))                                                                                                                                               
        (message "no screen session found."))))                                                                                                                                                
(define-key *root-map* (kbd "C-e") "emacs-in-screen")

For some reason this sometimes fails to switch to emacs properly, but it usually does!

And one last thing. The GNU Screen version shipped with Arch lacks vertical split support. This AUR package contains the patch for vertical splitting. Unfortunately, it lacks another patch that stops screen from complaining about long $TERM values, so I made a new AUR package that applies this other patch, too. I found that the process of creating Arch packages is surprisingly easy. In this case, I just downloaded the other package, updated its PKGFILE, and made the source tarball using makepkg --source.