How to delete empty subfolders

Suppose you have a folder with a lot of empty subfolders; in fact you don't know in which folder is the content you are looking for.

One way  is to use a gui application baobab or qdirstat
But even then creating order in the chaos will be a tedious job.
Go in terminal to the main folder and do
$find . -type d -empty -delete

Extract image from pdf file without quality loss to jpgs

Move in terminal to folder which contains the pdf file.

$pdfimages -j file.pdf page

This will leave you with .jpgs  for the image files 

and .pbm for the text pages.

Convert wit imagemagick installed the pbm files:

$convert *.pbm *.jpg

 

pkgcaccheclean replaces cachelean

Make room with pkgcacheclean in Arch

All installed packages will be cached in /var/cache/pacman/pkg
If you look in this cache you will be surprised to find as much as four or five versions of the same program.
If you want to make room than it is useful to purge the cache of too many versions of the same program with pkgcacheclean: https://aur.archlinux.org/packages/pkgcacheclean/
Do as root: #pkgcacheclean -v 
to actually do it.

Usage: pkgcacheclean [options] [number]

The default number is 2. That means, for all installed packages, the currently used version and the newest of the remaining cache is retained. All caches of not-installed packages are removed.
Currently, supported options only includes -v/--verbose, -q/--quiet, -n/--dry-run, -k/--all-as-installed.

more info