Weather webcams are always popular and it is easy and free to set one up yourself. This article will show how to setup a simple USB webcam to produce still images and serve them on a local apache webserver.
Category: Ubuntu
Formatting xml in emacs
I had this problem of debugging some xml but when reading the output of some log4j it was almost impossible to read so I needed some way of prettifying the xml quickly.
For this example I have the following xml:
<?xml version="1.0"?><xml><iq xmlns="jabber:component:accept" from="test1@temp.retep.org/client" id="iq_257" to="service.retep.org" type="get"><query xmlns="some:namespace"/></iq></xml>
So how do we pretify this in emacs?
Well the first thing to do is to write an extension function & place it into your ~/.emacs file. Placing it here means that when you open emacs the extension is available:
(defun xml-format ()
(interactive)
(save-excursion
(shell-command-on-region (mark) (point) "xmllint --format -" (buffer-name) t)
)
)
Now this works by passing the buffer to the xmllint utility and replaces it with the output – in this case nicely formatted xml.
Now we need to install xmllint:
pi@lindesfarne: ~$ sudo apt-get install libxml2-utils
Ok so now open emacs and open the xml. To format first select the xml you want to format then Press Escape then x followed by xml-format & press return. You should then get the xml nicely formatted:
<?xml version="1.0"?>
<xml>
<iq xmlns="jabber:component:accept" from="test1@temp.retep.org/client" id="iq_257" to="service.retep.org" type="get">
<query xmlns="some:namespace"/>
</iq>
</xml>
Using NFS to provide extra disk to a Raspberry PI
As the Raspberry PI uses an SD Card for it’s boot device there are times when you need either more space than is available on that device or a device that’s faster – writing to flash is slow and flash cards do have a limited number of writes that can be made to them.
Now there’s several ways to accomplish this:
- Use an external USB drive (the common route)
- Use a network shared drive
Using a USB drive is simple and is the faster option but it means it’s dedicated to the PI whilst it’s in use, hence this article on using a network drive – in this instance a directory on another Linux box in the network.
Also having it shared on the network means that multiple machines could use it at the same time. Imagine if you are a teacher with a collection of PI’s being used by your students. You could setup a central read-only directory with your class work which they can all access as if it’s installed locally.
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