Archiv für Oktober, 2016

Signing Firefox addons

24. Oktober 2016 Keine Kommentare

I’m heavy user of Pentadactyl – a Firefox addon which allows you to use a browser without a mouse. Occasionally I need to compile it from source to make it work on a new Firefox. In the past it could be used right away after compiling but since some time Mozilla requires all addons to be signed before they can be installed used in Firefox. Luckily it’s possible to sign an addon. It’s a simple and fast process but still a bit annoying. Signing is done with a tool called jpm provided by Mozilla. It can be installed with npm:

npm install jpm

Before using jpm to sign an addon you need to get a developer JSON Web Token issuer and secret token from The command is:

$ ./node_modules/jpm/bin/jpm sign --api-key 'user:<KEY>' --api-secret \
 '<API_SECRET>' --xpi pentadactyl-1.2pre.xpi

During this process you can get several different errors. Some of them are:

Server response: You do not own this addon. (status: 403)
JPM [info] FAIL

Replace em:id=“<EMAIL>“ in install.rdf inside your addon XPI file with e-mail address you used to register at

If you got this error:

Error: Received bad response from the server while requesting

status: 401
response: {"detail":"Unknown JWT iss (issuer)."}

You used incorrect API key/secret. Make sure that you used correct keys.

Error: Received bad response from the server while requesting

status: 401
response: {"detail":"JWT iat (issued at time) is invalid. Make sure your system clock is synchronized with something like TLSdate."}

Every call to Mozilla API relies on JSON web tokens which have an expiration time set. Make sure that you have your local time synchronized with one of ntp servers, for example:

sudo ntpdate

If you got this error:

JPM [info] Signing XPI: /home/ja/dactyl/downloads/pentadactyl-1.2pre.xpi
Server response: Version already exists. (status: 409)
JPM [info] FAIL

Replace em:version=<VERSION> in install.rdf with a new unique version.

After a successfully signing of your xpi jpm will automatically download it to your local machine. You can now install it in Firefox without any problems.

Kategorienfirefox Tags:

Lesser known uses of grep

23. Oktober 2016 Keine Kommentare

In this article i am going to present a couple of interesting and lesser known uses of grep. I am not going to list grep options because this is what manpage is for but instead show a couple of neat things that can be achieved with grep that seem useful but are not so straightforward. Let’s get started:

Show colored matches and the entire input

Sometimes it’s handy to see all matches in color together with the entire original input on one screen. For example, we have a long text divided in many sections and we want to read the whole section that contains a given match. We don’t when in a section a match will occur. We can’t use -A or -B options because not sections are the same length. To achieve what we want we can use grep like this:

$ man grep | grep --color=always -E 'pattern|' | less

This command will show the entire grep manpage will all occurrences of `pattern` in color.

Start grepping from nth line:

Sometimes we want to start grepping a file from n-th line, for example to omit a pre-defined header we don’t care about. We can do achieve that with a little help of `tail`. For example, to start searching for a string from 15th line:

$ tail +15 FILE | grep <PATTERN>

Detect line endings in a file:

We can use grep to detect line endings:

$ egrep -l $'\r'\$ *

The above command will return success if file contains carriage returns, that line endings used in Windows world. Note though that $’r‘ is a bash feature and might non work in other shells.

Kategoriencli, grep, linux Tags: