One of the problems with having external scripts on your site is that you have little control over them – caching and the like are out of your hands.
I’m no Linux expert (or probably even amateur, if I’m honest) so it took a while to find the right code to use, but here is the result…
wget -N --directory-prefix=[local folder] [script location]
[local folder] to where you wish the script to be copied to and
[script location] to where the external script is held (including script name). If you wish to perform multiple copies you can append them together with
So an example may be…
wget -N --directory-prefix=public_html/wp-content/themes/artiss http://pagead2.googlesyndication.com/pagead/show_ads.js
This would copy the AdSense code
show_ads.js to a theme folder named “artiss”.