# Introduction

## Quick Start

1. Run `urlwatch` once to migrate your old data or start fresh

2. Use `urlwatch --edit` to customize jobs and filters (`urls.yaml`)

3. Use `urlwatch --edit-config` to customize settings and reporters (`urlwatch.yaml`)

4. Add `urlwatch` to your crontab (`crontab -e`) to monitor webpages periodically

The checking interval is defined by how often you run `urlwatch`. You can use e.g. crontab.guru to figure out the schedule expression for the checking interval, we recommend not more often than 30 minutes (this would be `*/30 * * * *`). If you have never used cron before, check out the crontab command help.

On Windows, `cron` is not installed by default. Use the Windows Task Scheduler instead, or see this StackOverflow question for alternatives.

## How it works

Every time you run urlwatch(1), it:

- retrieves the output of each job and filters it

- compares it with the version retrieved the previous time (“diffing”)

- if it finds any differences, it invokes enabled reporters (e.g. text reporter, e-mail reporter, …) to notify you of the changes

## Jobs and Filters

Each website or shell command to be monitored constitutes a “job”.

The instructions for each such job are contained in a config file in the YAML format. If you have more than one job, you separate them with a line containing only `---`.

You can edit the job and filter configuration file using:

    urlwatch --edit

If you get an error, set your `$EDITOR` (or `$VISUAL`) environment variable in your shell, for example:

    export EDITOR=/bin/nano

While you can edit the YAML file manually, using `--edit` will do sanity checks before activating the new configuration file.

### Kinds of Jobs

Each job must have exactly one of the following keys, which also defines the kind of job:

- `url` retrieves what is served by the web server (HTTP GET by default),

- `navigate` uses a headless browser to load web pages requiring JavaScript, and

- `command` runs a shell command.

Each job can have an optional `name` key to define a user-visible name for the job.

You can then use optional keys to finely control various job’s parameters.

### Filters

You may use the `filter` key to select one or more Filters to apply to the data after it is retrieved, for example to:

- select HTML: `css`, `xpath`, `element-by-class`, `element-by-id`, `element-by-style`, `element-by-tag`

- make HTML more readable: `html2text`, `beautify`

- make PDFs readable: `pdf2text`

- make JSON more readable: `format-json`

- make iCal more readable: `ical2text`

- make binary readable: `hexdump`

- just detect changes: `sha1sum`

- edit text: `grep`, `grepi`, `strip`, `sort`, `striplines`

These filters can be chained. As an example, after retrieving an HTML document by using the `url` key, you can extract a selection with the `xpath` filter, convert this to text with `html2text`, use `grep` to extract only lines matching a specific regular expression, and then `sort` them:

    name: "Sample urlwatch job definition"
    url: "https://example.dummy/"
    https_proxy: "http://dummy.proxy/"
    max_tries: 2
    filter:
      - xpath: '//section[@role="main"]'
      - html2text:
          method: pyhtml2text
          unicode_snob: true
          body_width: 0
          inline_links: false
          ignore_links: true
          ignore_images: true
          pad_tables: false
          single_line_break: true
      - grep: "lines I care about"
      - sort:
    ---

## Reporters

urlwatch can be configured to do something with its report besides (or in addition to) the default of displaying it on the console.

Reporters are configured in the global configuration file:

    urlwatch --edit-config

Examples of reporters:

- `email` (using SMTP)

- email using `mailgun`

- `slack`

- `discord`

- `pushbullet`

- `telegram`

- `matrix`

- `pushover`

- `stdout`

- `xmpp`

- `shell`