It is nice to have a desktop wallpaper that is not static, I like to see some outdoor scene that has a good view and a dynamic sky. Wyoming certainly has some ever changing skies and nice terrain so I have a wallpaper background set to show the Cloud Peaks Wilderness in Wyoming that updates every hour.

It is possible to load a JPG file periodically from a source using the Linux built-in wget command. In the example below, I am loading a scene from Cloud Peak Wyoming that is captured by a US Forest Service Webcam. It is loading right into my home folder, it could be put in any place that you prefer.

There is a nice bunch of pictures taken by the Forest Service from all over the country and they provide some nice high resolution scenery. See the links at the bottom of this post.

Code for script file

#! /bin/bash
 rm /home/erick/cpwa1_large.jpg
 wget http://www.fsvisimages.com/images/photos-large/cpwa1_large.jpg

The code first removes the old copy of the image and then it uses the wget command to fetch a new copy.

.wgetrc

It is not necessary to modify .wgetrc to use wget, but I put this here as an FYI. There is a configuration file for wget. It is located at /usr/local/etc/wgetrc. More info on wget locations. You can make a copy of it and put it in your home directory. Once in the home directory any modifications to it will work for your user profile. I have mine modified to do a few non-standard things, one is to use timestamping which will make wget only download when the file it is trying to download is newer than the local copy.

# Set this to on to use timestamping by default:
timestamping = on

Secondly, I also added a line at the end of the file that puts an option for wget for limiting the rate of downloading. Otherwise wget will run as fast as possible and will use the entire bandwidth. This option can be used on a case by case basis by putting in the line when wget is called as well. Doing this makes it so wget doesn’t slow down your connection to the Internet a lot and doesn’t hit the server hard with high speed downloads, important if you are downloading multiple large files.

limit-rate=20k

It is also possible to add a bit of a delay between connections when downloading. This avoids hammering the server that you are downloading from when downloading multiple files. This makes it easier on the server load and makes your download activity less likely to be obnoxious to the folks running the server that you are downloading from. Obnoxious down-loaders and site scrapers are more likely to get banned I would imagine if someone notices a spike in server load and pins it down to the IP address.

# It can be useful to make Wget wait between connections.  Set this to
# the number of seconds you want Wget to wait.
wait = 1

Some sites go as far as prohibiting downloads unless the user agent has a string inside of it. I didn’t do this yet as I have not had a problem with this issue. But it is possible to set the user-agent via --user-agent=“Acceptable String Here”

More on user-agent modification

CRON entry

01 08-22 * * * /home/erick/cpwa1/wget-cpwa1.sh

Using crontab -e, a line can be loaded into your CRON file to run the script periodically. The one above runs every hour 1 minute after the hour between 8AM and 10PM. There is no sense in loading nighttime pictures so that is why the times are bounded to load pictures during daylight hours ( right now) for Mountain Daylight Time. The picture I load is update around 59 minutes after the hour so loading 1 minute after the hour provides a bit of a guard band of time.

USDA Forest Service Webcams

USDA Forest Service Real Time Image Description Page
USDA Forest Service Real Time Image Gallery