livecheck.md

livecheck

The livecheck stanza is used to automatically fetch the latest version of a cask from changelogs, release notes, appcasts, etc.

Every livecheck block must contain a url, which can either be a string or a symbol pointing to other URLs in the cask (:url or :homepage).

Additionally, a livecheck should specify which strategy should be used to extract the version:

strategy	Description
:header_match	extract version from HTTP headers (e.g. Location or Content-Disposition)
:page_match	extract version from page contents
:sparkle	extract version from Sparkle appcast contents

Here is a basic example, extracting a simple version from a page:

livecheck do
  url "https://example.org/my-app/download"
  strategy :page_match
  regex(%r{href=.*?/MyApp-(\d+(?:\.\d+)*)\.zip}i)
end

If the download URL is present on the homepage, we can use a symbol instead of a string:

livecheck do
  url :homepage
  strategy :page_match
  regex(%r{href=.*?/MyApp-(\d+(?:\.\d+)*)\.zip}i)
end

The header_match strategy will try parsing a version from the filename (in the Content-Disposition header) and the final URL (in the Location header). If that doesn't work, a regex can be specified, e.g.:

strategy :header_match
regex(/MyApp-(\d+(?:\.\d+)*)\.zip/i)

If the version depends on multiple header fields, a block can be specified, e.g.

strategy :header_match do |headers|
  v = headers["content-disposition"][/MyApp-(\d+(?:\.\d+)*)\.zip/i, 1]
  id = headers["location"][%r{/(\d+)/download$}i, 1]
  "#{v},#{id}"
end

Similarly, the :page_match strategy can also be used for more complex versions by specifying a block:

strategy :page_match do |page|
  match = page.match(%r{href=.*?/(\d+)/MyApp-(\d+(?:\.\d+)*)\.zip}i)
  "#{match[2]},#{match[1]}"
end