Provided by: urlwatch_2.25-1_all 
NAME
urlwatch-cookbook - Advanced topics and recipes for urlwatch
ADDING URLS FROM THE COMMAND LINE
Quickly adding new URLs to the job list from the command line:
urlwatch --add url=http://example.org,name=Example
USING WORD-BASED DIFFERENCES
You can also specify an external diff-style tool (a tool that takes two filenames (old,
new) as parameter and returns on its standard output the difference of the files), for
example to use wdiff(1) to get word-based differences instead of line-based difference:
url: https://example.com/
diff_tool: wdiff
Note that diff_tool specifies an external command-line tool, so that tool must be
installed separately (e.g. apt install wdiff on Debian or brew install wdiff on macOS).
Coloring is supported for wdiff-style output, but potentially not for other diff tools.
IGNORING CONNECTION ERRORS
In some cases, it might be useful to ignore (temporary) network errors to avoid
notifications being sent. While there is a display.error config option (defaulting to
true) to control reporting of errors globally, to ignore network errors for specific jobs
only, you can use the ignore_connection_errors key in the job list configuration file:
url: https://example.com/
ignore_connection_errors: true
Similarly, you might want to ignore some (temporary) HTTP errors on the server side:
url: https://example.com/
ignore_http_error_codes: 408, 429, 500, 502, 503, 504
or ignore all HTTP errors if you like:
url: https://example.com/
ignore_http_error_codes: 4xx, 5xx
OVERRIDING THE CONTENT ENCODING
For web pages with misconfigured HTTP headers or rare encodings, it may be useful to
explicitly specify an encoding from Python’s Standard Encodings
<https://docs.python.org/3/library/codecs.html#standard-encodings>.
url: https://example.com/
encoding: utf-8
CHANGING THE DEFAULT TIMEOUT
By default, url jobs timeout after 60 seconds. If you want a different timeout period, use
the timeout key to specify it in number of seconds, or set it to 0 to never timeout.
url: https://example.com/
timeout: 300
SUPPLYING COOKIE DATA
It is possible to add cookies to HTTP requests for pages that need it, the YAML syntax for
this is:
url: http://example.com/
cookies:
Key: ValueForKey
OtherKey: OtherValue
COMPARING WITH SEVERAL LATEST SNAPSHOTS
If a webpage frequently changes between several known stable states, it may be desirable
to have changes reported only if the webpage changes into a new unknown state. You can use
compared_versions to do this.
url: https://example.com/
compared_versions: 3
In this example, changes are only reported if the webpage becomes different from the
latest three distinct states. The differences are shown relative to the closest match.
RECEIVING A REPORT EVERY TIME URLWATCH RUNS
If you are watching pages that change seldomly, but you still want to be notified daily if
urlwatch still works, you can watch the output of the date command, for example:
name: "urlwatch watchdog"
command: "date"
Since the output of date changes every second, this job should produce a report every time
urlwatch is run.
USING REDIS AS A CACHE BACKEND
If you want to use Redis as a cache backend over the default SQLite3 file:
urlwatch --cache=redis://localhost:6379/
There is no migration path from the SQLite3 format, the cache will be empty the first time
Redis is used.
WATCHING CHANGES ON .ONION (TOR) PAGES
Since pages on the Tor Network <https://www.torproject.org> are not accessible via public
DNS and TCP, you need to either configure a Tor client as HTTP/HTTPS proxy or use the
torify(1) tool from the tor package (apt install tor on Debian, brew install tor on
macOS). Setting up Tor is out of scope for this document. On a properly set up Tor
installation, one can just prefix the urlwatch command with the torify wrapper to access
.onion pages:
torify urlwatch
WATCHING FACEBOOK PAGE EVENTS
If you want to be notified of new events on a public Facebook page, you can use the
following job pattern, replace PAGE with the name of the page (can be found by navigating
to the events page on your browser):
url: http://m.facebook.com/PAGE/pages/permalink/?view_type=tab_events
filter:
- css:
selector: div#objects_container
exclude: 'div.x, #m_more_friends_who_like_this, img'
- re.sub:
pattern: '(/events/\d*)[^"]*'
repl: '\1'
- html2text: pyhtml2text
ONLY SHOW ADDED OR REMOVED LINES
The diff_filter feature can be used to filter the diff output text with the same tools
(see filters) used for filtering web pages.
In order to show only diff lines with added lines, use:
url: http://example.com/things-get-added.html
diff_filter:
- grep: '^[@+]'
This will only keep diff lines starting with @ or +. Similarly, to only keep removed
lines:
url: http://example.com/things-get-removed.html
diff_filter:
- grep: '^[@-]'
More sophisticated diff filtering is possibly by combining existing filters, writing a new
filter or using shellpipe to delegate the filtering/processing of the diff output to an
external tool.
Read the next section if you want to disable empty notifications.
DISABLE EMPTY NOTIFICATIONS
As an extension to the previous example, let's say you want to only get notified with all
lines added, but receive no notifications at all if lines are removed.
A diff usually looks like this:
--- @ Fri, 04 Mar 2022 19:58:14 +0100
+++ @ Fri, 04 Mar 2022 19:58:22 +0100
@@ -1,3 +1,3 @@
someline
-someotherlines
+someotherline
anotherline
We want to filter all lines starting with "+" only, but because of the headers we also
want to filter lines that start with "+++", which can be accomplished like so:
url: http://example.com/only-added.html
diff_filter:
- grep: '^[+]' # Include all lines starting with "+"
- grepi: '^[+]{3}' # Exclude the line starting with "+++"
This deals with all diff lines now, but since urlwatch reports "changed" pages even when
the diff_filter returns an empty string (which might be useful in some cases), you have to
explicitly opt out by using urlwatch --edit-config and setting the empty-diff option to
false in the display category:
display:
empty-diff: false
PASS DIFF OUTPUT TO A CUSTOM SCRIPT
In some situations, it might be useful to run a script with the diff as input when changes
were detected (e.g. to start an update or process something). This can be done by
combining diff_filter with the shellpipe filter, which can be any custom script.
The output of the custom script will then be the diff result as reported by urlwatch, so
if it outputs any status, the CHANGED notification that urlwatch does will contain the
output of the custom script, not the original diff. This can even have a "normal" filter
attached to only watch links (the css: a part of the filter definitions):
url: http://example.org/downloadlist.html
filter:
- css: a
diff_filter:
- shellpipe: /usr/local/bin/process_new_links.sh
SETTING THE CONTENT WIDTH FOR HTML2TEXT (LYNX METHOD)
When using the lynx method in the html2text filter, it uses a default width that will
cause additional line breaks to be inserted.
To set the lynx output width to 400 characters, use this filter setup:
url: http://example.com/longlines.html
filter:
- html2text:
method: lynx
width: 400
COMPARING WEB PAGES VISUALLY
To compare the visual contents of web pages, Nicolai has written pyvisualcompare
<https://github.com/nspo/pyvisualcompare> as a frontend (with GUI) to urlwatch. The tool
can be used to select a region of a web page. It then generates a configuration for
urlwatch to run pyvisualcompare and generate a hash for the screen contents.
CONFIGURING HOW LONG BROWSER JOBS WAIT FOR PAGES TO LOAD
For browser jobs, you can configure how long the headless browser will wait before a page
is considered loaded by using the wait_until option. It can take one of four values:
• load will wait until the load browser event is fired (default).
• documentloaded will wait until the DOMContentLoaded browser event is fired.
• networkidle0 will wait until there are no more than 0 network connections for at
least 500 ms.
• networkidle2 will wait until there are no more than 2 network connections for at
least 500 ms.
TREATING NEW JOBS AS CHANGED
In some cases (e.g. when the diff_tool or diff_filter executes some external command as a
side effect that should also run for the initial page state), you can set the
treat_new_as_changed to true, which will make the job report as CHANGED instead of NEW the
first time it is retrieved (and the diff will be reported, too).
url: http://example.com/initialpage.html
treat_new_as_changed: true
This option will also change the behavior of --test-diff-filter, and allow testing the
diff filter if only a single version of the page has been retrieved.
MONITORING THE SAME URL IN MULTIPLE JOBS
Because urlwatch uses the url/navigate (for URL/Browser jobs) and/or the command (for
Shell jobs) key as unique identifier, each URL can only appear in a single job. If you
want to monitor the same URL multiple times, you can append #1, #2, ... (or anything that
makes them unique) to the URLs, like this:
name: "Looking for Thing A"
url: http://example.com/#1
filter:
- grep: "Thing A"
---
name: "Looking for Thing B"
url: http://example.com/#2
filter:
- grep: "Thing B"
RUNNING A SUBSET OF JOBS
To run one or more specific jobs instead of all known jobs, provide the job index numbers
to the urlwatch command. For example, to run jobs with index 2, 4, and 7:
urlwatch 2 4 7
SENDING HTML FORM DATA USING POST
To simulate submitting a HTML form using the POST method, you can pass the form fields in
the data field of the job description:
name: "My POST Job"
url: http://example.com/foo
data:
username: "foo"
password: "bar"
submit: "Send query"
By default, the request will use the HTTP POST method, and the Content-type will be set to
application/x-www-form-urlencoded.
SENDING ARBITRARY DATA USING HTTP PUT
It is possible to customize the HTTP method and Content-type header, allowing you to send
arbitrary requests to the server:
name: "My PUT Request"
url: http://example.com/item/new
method: PUT
headers:
Content-type: application/json
data: '{"foo": true}'
SEE ALSO
urlwatch(1), urlwatch-intro(7), urlwatch-jobs(5), urlwatch-filters(5), urlwatch-config(5),
urlwatch-reporters(5)
COPYRIGHT
2022 Thomas Perl