For a few months now, I have been using my
watch-diff project to get notified on
command output changes. The beauty of this simple tool is that it works with any
command that can be executed in the shell. This means that once you figure out
the exact command you need to monitor, you simply plug it into
you automatically get email notifications on updates.
Example: monitoring current releases
Here is the output for monitoring the current version of this package on the PyPI website while a release is being made:
$ watch-diff "curl -s https://pypi.org/project/watch-diff/ | \ sed -n '/<h1 class=\"package-header__name\">/,/<\/h1>/p'" [2020-03-01 01:04:11.697054] first_run: <h1 class="package-header__name"> watch-diff 1.0.2 </h1> [2020-03-01 01:04:16.839766] no diff [2020-03-01 01:04:21.986465] no diff [2020-03-01 01:04:27.122121] no diff [2020-03-01 01:04:32.278194] no diff [2020-03-01 01:04:37.424123] diff: --- Previous 2020-03-01 01:04:32.278194 +++ Current 2020-03-01 01:04:37.424123 @@ -1,3 +1,3 @@ <h1 class="package-header__name"> - watch-diff 1.0.2 + watch-diff 1.0.3 </h1> [2020-03-01 01:04:42.710685] no diff ...
No extra dependencies
This Python package does not require any extra PyPI packages to function. Instead, it relies on a few packages from the Standard Library. These include:
argparse: Handle arguments passed to the CLI command.
datetime: Manage timestamps for command runs.
difflib: Get nice looking diffs of command outputs.
smtplib: Communication with SMTP server.
subprocess: Calling the actual command and reading the output.
Since there aren’t any additional packages installed with
isn’t much danger in installing it globally with
pip as a regular user. This
has the advantage of being able to call it from wherever without having to worry
about a virtual environment.
# install as user in home directory pip install --user watch-diff
Email thread handling
By setting the
In-Reply-To in the emails sent, they are
easily grouped together in their respective runs. This makes it possible to
start multiple instances of
watch-diff all watching different commands while
keeping a tidy inbox.
Mar 01 2020 watch-diff (2.8K) ┌─> Mar 01 2020 watch-diff (2.9K) ┌─>watch-diff diff: ls -la Mar 01 2020 watch-diff (7.5K) watch-diff first_run: ls -la Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─> Mar 01 2020 watch-diff (1.6K) ┌─>watch-diff diff: date Mar 01 2020 watch-diff (1.3K) watch-diff first_run: date
watch-diff is only needed if the
-r/--recipient option is
used. This triggers email notifications and so SMTP settings are needed. If
used, the program will either prompt the user for the needed values or use the
ones set in environment variables if available. The following variables are
These can be exported in the
~/.bashrc file so they are available at any time.
A good strategy for more secure configuration is to create an email account that
is used exclusively for sending emails. If the credentials get compromised, it
is has less impact than if your main email credentials get stolen. Also, it is a
good idea to use
secret-tool lookup ... to get the SMTP password so that it is
not written in plain text in a config file.
I am very satisfied with this tool right now; it is super simple to use with whatever shell command, the emails are tidy and they look good. If you have any issues or want to suggest or contribute a feature, feel free to contact me!