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Every so often I find a need for some small script that will reduce or eliminate some annoyance.

One case is running out of disk space. I really could not tell you what in the world is consuming my laptop drive, but 200G is evidently not enough.

Every so often I think to check the amount of free space, and move off or delete this or that. But sometimes I suddenly find myself with zero free space, and some applications just don’t handle this well.

I decided to create a cron task that would check the disk usage and warn me when free space fell below some set amount.

The Ruby code was simple (though potentially hackish. If there’s a better way to get the amount of free disk I’d like to hear of it).

Here’s grabbing the disk space

def free_diskspace drive
  results = `df -h #{drive}`
  # Filesystem         Size  Used Avail Use% Mounted on
  data = results.split( "\n").last.split(' ')
  value = data[3]
  value.sub!( /G$/, '')
  value
end
 

To issue an alert when space is low, I used KDE’s built-in kdialog command. There’s a Ruby lib that wraps this, but invoking it directly is simple enough.

def alert msg
    puts `kdialog  --display :0 --error "#{msg}"`
end
 

The logic is basic:

space = free_diskspace '/dev/sda1' 
alert "Running low on disk space: #{space}"  if space.to_f < 2.0

One point that wasn’t obvious when I wrote this: the cron task may not be using the same X display as the user, so the message box may not be seen. The fix is the explicit use of --display :0 when calling kdialog.