Scriptable tmux status line

devops
, ,

tmux is awsome, but creating scripts for the status line is a lot of work. I’ve looked into different scripts at the tmux-plugins repo and saw a recurring pattern. Or dare I say, a lot of copy-n-pasting of the same code from one plugin to another. Many of them lay the same groundwork:

  • Add utils function to get or set tmux options
  • Add code that transforms the status line and calls the scripts
  • Add a caching layer to make sure no redudant calls are made

I’ve taken the liberty to create a plugin, tmux-status-variables, that helps creating and using status line scripts extremely easy.

A regular plugin only needs to have execution priviledges.
For instance, lets look at this hello world plugin:

#!/bin/bash  
echo "hello world!"

If hello world takes a lot of time, we might want to cache the result.
Results are cached for status-interval seoconds. lets look at the following plugin:

 #!/bin/bash  
 PLUGIN_DIR=$(tmux show-option -gqv "@status_variables_dir")  
 source "$PLUGIN_DIR/utils/sdk.sh"

on_cache_miss() {  
  echo "hello world!"  
  sleep 1  
}

echo "$(get_cached_value on_cache_miss)"

on_cache_miss will run only when status-interval seconds have passed.
This is important because tmux might refreshes the status line when redrawing the pane.
Every time you press or create a new pane, the status line is refreshed which causes many script calls.

Now all that’s left is to run it:

  • Dump the content of the script to the scripts_directory, and name it hello.tmux
  • Add set -g status-left "#{hello}" to your tmux.conf and your good to go!