About swk

I am a software developr, data scientist, computational linguist, teacher of computer science and above all a huge fan of LaTeX. I use LaTeX for everything, including things you never wanted to do with LaTeX. My latest love is lilypond, aka LaTeX for music. I'll post at irregular intervals about cool stuff, stupid hacks and annoying settings I want to remember for the future.

Throw away your change and reset a git branch to remote

Sometimes, you do something really stupid and just want to get rid of it. Or you are suddenly in the middle of a complicated merge and don’t really know why anymore (“But I didn’t change anything!”). In this case, if you are sure you want to throw away everything in your local branch and just want to be at the same status as the remote branch, this is your rescue:

git reset --hard origin/<branchname>

But be careful, the --hard option deletes all changes that you have made without recovery.

Spendenbescheinigung mit jVerein erstellen

Um eine Spendenbescheinigung automatisch erzeugen zu können, muss die Buchung korrekt als Spende markiert sein und einem Mitglied zugeordnet sein. Das geht folgendermaßen:
1. Unter “JVerein – Buchführung – Buchungen” die entsprechende Buchung finden und in die Detailansicht gehen.
2. Buchungsart “Spende” (oder wie auch immer die entsprechende Kategorie heißt) auswählen. Bei “Mitgliedskonto” die Punkte klicken, auf den Tab “Soll und Ist” und unten in der Tabelle die korrekte Person auswählen (dort lief eine Suche über die Mitglieder nach dem Namen auf der Überweisung, falls da nicht das korrekt Mitglied gefunden wurde – oh je!). Als Ergebnis steht jetzt im Feld “Name, Sollbuchung erzeugen”

Wenn das bei allen Buchungen korrekt verbucht wurde, können die Bescheinigungen erzeugt werden. Das geht so:
1. “JVerein – Spendenbescheinigungen”
2. Unten “neu (automatisch)” klicken.
3. Korrektes Jahr und Vorlage auswählen. Dann sollte unten eine Liste der Spenden erscheinen.
3. Auf “erstellen” klicken.
4. Jetzt sollten die entsprechenden Einträge unter “Spendenbescheinigungen” auffindbar sein. Jeden Eintrag dort auswählen und einmal auf “speichern” klicken und den Eintrag wieder schließen (unbedingt nötig!!!)
5. Den Eintrag neu öffnen und mit “pdf (individuell)” ein pdf mit der Spendenbescheinigung erzeugen lassen.

Nun kann die Bescheinigung gedruckt, verschickt oder was auch immer werden.

Clean Spark environment in Zeppelin

When you have experimented a lot, there are many things in your notebook and quite often, you are not sure what is there and what not. Zeppelin does not really give you a good tool to do that, so I wrote my own function to clean up the global variables of Python:

def clear(keep=("__builtins__", "clear", 'completion', 'z', '__zeppelin_completion__', '_zsc_', '__zSqlc__', '__zeppelin__', '__zSpark__', 'sc', 'spark', 'sqlc', 'sqlContext')):
    keeps = {}
    for name, value in globals().iteritems():
        if name in keep: 
            keeps[name] = value
    for name, value in keeps.iteritems():
        globals()[name] = value

You can then call the function with clear().

Additionally, if you are dealing with libraries, you may want to explicitly remove them with del sys.modules['modulename'].

Cloudformation templates for existing resources

You can use the AWS CLI to get a description of existing resources. This description is in JSON format, which can sometimes directly be used as a Cloudformation template.


aws glue get-job --job-name MyJobName

Makes the job easier! For example with the Glue job, we can see the undocumented options

"--enable-metrics": ""
"--TempDir": "s3://blablubbtest"
"--enable-continuous-cloudwatch-log": "true"

So since Cloudformation is a pain to debug, a possible way to write a template might be to click together the resources with the Console, then get the description with the CLI and use this to create the resources with Cloudformation next time.

Disable graphical prompt for ssh passphrase

When I open a ssh session in the terminal, it asks for my passphrase in a graphical prompt window. That would be ok in theory. But I don’t know my passphrase. So I need to copy it from my password manager. And unfortunately the stupid window doesn’t allow me to access anything else. So, I wanted to disable it.

The usual way is with the environment variable SSH_ASKPASS. To disable the graphical prompt, just remove the value of this variable:


Unfortunately, in my case this did not work and I needed to remove also another variable:


Pip and custom prefixes… again! This time it’s Ubuntu’s fault

I wanted to install a Python library to a custom location. Thanks to a long fight with Python on that issue (I can’t believe I haven’t blogged about this!), I know that --prefix does the trick for pip. So I run pip and this happens:

> pip3 install --prefix tmp/ boto3
ERROR: Can not combine '--user' and '--prefix' 
as they imply different installation locations

Alternatively the error is:

distutils.errors.DistutilsOptionError: can't combine user
with prefix, exec_prefix/home, or install_(plat)base

It seems to be an option that Ubuntu adds by default. The magic solution comes from a GNU bug tracker thread:

> pip3 install -U pip

Basically, this installs pip into my user directory (you can find it now in .local/bin/pip). pip3 still fail afterwards with a version mismatch:

> pip3 install --prefix tmp/ boto3
Traceback (most recent call last):
  File "/usr/bin/pip3", line 9, in <module>
    from pip import main
ImportError: cannot import name 'main'

But now I can call my local pip (which is a pip3):

> pip install --prefix tmp/ boto3
Collecting boto3
Successfully installed boto3-1.9.206 botocore-1.12.206

To force a re-install, even if the library is already installed somewhere else, use the flag --ignore-installed.

Add shared Exchange calender to Evolution Mail

I just spent a lot of time searching, so I really need to make sure not to forget this. I want to see a colleague’s calendar. Everything is in Office 365, so I have no problem adding the calendar in the web interface. Naive me thought, this will cause Evolution Mail to show the calendar also. Nope.

I searched for a way to add a calendar in the calendar view of Evolution. With right click on the account or in some menu. Nope. I can add calendars for myself, but not get a colleague’s calendar. Of course. That would have been too easy!

So what does work? Thank you jldugger:

On the Mail view, right click your exchange account, select “Subscribe to folder of other EWS user.” Type in the name of the account you want, and choose “Calendar” from the dropdown.

For me “Free/Busy as Calendar” worked, “Calendar” did not.

Copy your pictures from iPhone with Linux

First, you will need to install iFuse:

sudo apt install iFuse

Then, it is really simple:
1. Connect your iPhone with USB to your laptop.
2. Unlock your iPhone.
2. Run idevicepair pair.
3. The phone will ask if you want to trust this computer, say yes.
3. Open the folder Dolphin/file browser. For me, I get a “open camera” notification that leads me to the picture folder in the file browser. You can also try camera://<id given by idevicepair> or afc://<id given by idevicepair>.
4. Copy the files!

When I did this, I had to reset the connection with idevicepair a few times, but other than that it worked very well.

If this does not work for you, try this very thorough guide by Dedoimedo/Igor Ljubuncic: How to access iPhone (6s) with iOS 11 in Linux

Tree view in Nautilus on Ubuntu 18.04

Someone thought it a good idea to remove the settings dialogue in Nautilus. Whatever. Here is how to set “list view” as default and enable tree view:

gsettings set org.gnome.nautilus.preferences default-folder-viewer 'list-view'
gsettings set org.gnome.nautilus.list-view use-tree-view true