Fishy prompt widgets

23 April 2015 - Reading time: 3 minutes

Fish is a nice shell, its nice, lite, fast, and have a lot of features. One of them is universal variables. This variables are shared across sessions. This is very useful when I want to have a nice handy information in the prompt. We don’t want to execute command every time thats prompt appears. Lets use them.

This is what I’m talking about!

fish widgets

Widgets are refreshed in background, lets use cron. Write a little script that gather system information and set some variable that can be displayed in prompt. Create a ~/.config/fish/functions/

_prompt_info_status_for function takes 3 parameters:

  • a name of widget
  • how often we want to refresh widget
  • command line

I’ve got one for you here it is:

function _prompt_info_status_for
  set prompt_info_variable prompt_info_$argv[1]
  set prompt_info_interval $argv[2]
  set prompt_info_cmd $argv[3]

  function _prompt_info_status_current_time
    date "+%s"

  function _eval
    set result (eval $argv[1])
    if test -n result
      echo $result
      echo ''

  if set -q $prompt_info_variable
    if test (math (_prompt_info_status_current_time) - $$prompt_info_variable[1][2] ) -ge $prompt_info_interval
      set -U $prompt_info_variable[1][2] (_prompt_info_status_current_time)
      set -U $prompt_info_variable[1][1] (_eval $prompt_info_cmd)
    set -U $prompt_info_variable[1][2] (_prompt_info_status_current_time)
    set -U $prompt_info_variable[1][1] (_eval $prompt_info_cmd)
  echo $$prompt_info_variable[1][1]

Great. Lets set some widgets!!! I’m on OSX, lets use emoji as icons. We create 5 widgets:

  • battery status
  • free disk space
  • free memory
  • number of outdated brew package (refreshed once a day)
  • internet connection check

This is so simple too. Gather information first, and glue our propry variable. prompt_info this is a good name ;) Use some conditional, we don’t want brew icon when we up to date, and display nothing when there are internet connection. Look, this is it:

function prompt_info_update --description "Update system information in prompt"
  _prompt_info_status_for battery (math '60 * 1  * 1 ') 'pmset -g batt | egrep "([0-9]+\%).*" -o --colour=auto | cut -f1 -d";"'
  _prompt_info_status_for disk    (math '60 * 1  * 1 ') 'df -h / | tail -n1|  awk "{ gsub(/i/,\"\"); print \$4 }"'
  _prompt_info_status_for memory  (math '60 * 1  * 1 ') 'top -l1 -s0 -n1 | awk "/PhysMem/ {print \$6}"'
  _prompt_info_status_for brew    (math '60 * 60 * 24') 'brew update > /dev/null; brew outdated | wc -l | tr -d "[[:space:]]"'
  _prompt_info_status_for ping    (math '60 * 1  * 1 ') 'ping -c1 > /dev/null ; and echo "OK"'

  set -U prompt_info ""

  if test -n $prompt_info_battery[1]
    set -U prompt_info "$prompt_info🔋 $prompt_info_battery[1] "

  set -U prompt_info "$prompt_info📚 $prompt_info_memory[1] 💾 $prompt_info_disk[1] "

  if test $prompt_info_brew[1] -gt 0
    set -U prompt_info "$prompt_info🍺 $prompt_info_brew[1] "

  if not test -n $prompt_info_ping[1]
    set -U prompt_info "$prompt_info🚫  "

Lets display in the right prompt.

function fish_right_prompt
  echo $prompt_info

At the end, we need add something that updates our widgets.

$ crontab -e

and add

* * * * * /usr/local/bin/fish -c 'prompt_info_update'

And voila. Nice handy prompt widgets with about 50 LOC Another great stuff, quick and useful.