Tanguy Ortolo

This is one thing I have wanted to do for a long time: configure Mutt to encrypt all messages sent to addresses for which I have a valid public key. Well, here is an awk-based script to generate that configuration.

(Yes, I know, a similar script was already written. But I did not see it at first, and I find mine more readable. :-) )

Read more Mutt: encrypt all messages sent to known PGP users

A strange problem

Yesterday, I was reported a funny problem with the dokuwiki Debian package's postinst script, which contains a piece of shell script similar to that:

# Check the destination does not already exist
if [ ! -e /the/destination ]
then
    ln -s /some/file /the/destination
fi

It was failing with that message: ln: failed to create symbolic link '/the/destination': File exists. Even though I had just tested it did not exist!

Read more Beware of symlinks when testing a file existence

Like it or not, XML has been used everywhere, even in cases where text-based formats would have been sufficient. Unfortunately, standard tools such as grep, sed or awk are not really adapted to work with XML. Let us take the following example:

<chapter
    xmlns="http://docbook.org/ns/docbook" version="5.0">
    <title>The Debian distribution</title>

    <para>Debian is a free operating system, describing itself as “the
    universal operating system”. It is mostly known as a GNU/Linux
    distribution, but it also exist in other variants such as GNU/Hurd
    and GNU/kFreeBSD…</para>
</chapter>

Read more Working with XML using standard Unix tools

grep is designed to print lines matching a given pattern, but I often need to print only the matching part, discarding the remaining.

I used to do that with sed, but it involves several actions: match, replace the line by only the matching pattern and print. Fortunately, GNU grep has an option to do just that:

-o, --only-matching

Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.

Unfortunately it is not a standard option, so it may be missing on non-GNU systems.

UPower for regular users

Major desktop environments usually provide a user-friendly menu to suspend your computer. Internally, if seems to use something called UPower, which uses something called PolicyKit, which in turn may or may not use another piece called ConsoleKit (do not ask me what all these pieces are and how they relate to each other, I do not know and I do not want to know). For the regular user, the result is the following: when they click on that button, it suspends their computer.

Read more Suspend your computer from a non-mainstream desktop environment