NOTE: I am putting my support behind the {crrri} package and you should, too.
Headless ‘Chrome’ Orchestration
The ‘Chrome’ browser https://www.google.com/chrome/ has a headless mode which can be instrumented programmatically. Tools are provided to perform headless ‘Chrome’ instrumentation on the command-line, including retrieving the javascript-executed web page, PDF output or screen shot of a URL.
You'll need to set an envrionment variable HEADLESS_CHROME to use this package.
If this value is not set, a location heuristic is used on package start which looks for the following depending on the operating system:
- Windows(32bit):
C:/Program Files/Google/Chrome/Application/chrome.exe - Windows(64bit):
C:/Program Files (x86)/Google/Chrome/Application/chrome.exe - macOS:
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome - Linux:
/usr/bin/google-chrome
If a verification test fails, you will be notified.
It is HIGHLY recommended that you use decapitated::download_chromium() to use
a standalone version of Chrome with this packge for your platform.
It's best to use ~/.Renviron to store this value.
Security restrictions on various operating systems and OS configurations
can cause headless Chrome execution to fail. As a result, headless
Chrome operations should use a special directory for decapitated
package operations. You can pass this in as work_dir. If work_dir is
NULL a .rdecapdata directory will be created in your home directory
and used for the data, crash dumps and utility directories for Chrome
operations.
tempdir() does not always meet these requirements (after testing on
various macOS 10.13 systems) as Chrome does some interesting attribute
setting for some of its file operations.
If you pass in a work_dir, it must be one that does not violate OS
security restrictions or headless Chrome will not function.
The three core functions have a prime parameter. In testing (again,
especially on macOS), I noticed that the first one or two requests to a
URL often resulted in an empty <body> response. I don’t use Chrome as
my primary browser anymore so I’m not sure if that has something to do
with it, but requests after the first one or two do return content. The
prime parameter lets you specify TRUE, FALSE or a numeric value
that will issue the URL retrieval multiple times before returning a
result (or generating a PDF or PNG). Until there is more granular
control over the command-line execution of headless Chrome.
The following functions are implemented:
downlaod_chromium: Download a standalone version of Chromium (recommended)chrome_dump_pdf: "Print" to PDFchrome_read_html: Read a URL via headless Chrome and return the raw or rendered '' 'innerHTML' DOM elementschrome_shot: Capture a screenshotchrome_version: Get Chrome versionget_chrome_env: get an envrionment variable 'HEADLESS_CHROME'set_chrome_env: set an envrionment variable 'HEADLESS_CHROME'
Helpers to get gepetto installed:
install_gepetto: Install gepettostart_gepetto: Start/stop gepettostop_gepetto: Start/stop gepetto
API interface functions:
gepetto: Create a connection to a Gepetto API servergep_active: Get test whether the gepetto server is activegep_debug: Get "debug-level" information of a running gepetto servergep_render_har: Render a page in a javascript context and serialize to HARgep_render_html: Render a page in a javascript context and serialize to HTMLgep_render_magick: Render a page in a javascript context and take a screenshotgep_render_pdf: Render a page in a javascript context and rendero to PDF
More information on gepetto is forthcoming but you can take a sneak peek here.
devtools::install_github("hrbrmstr/decapitated")library(decapitated)
# current verison
packageVersion("decapitated")## [1] '0.3.0'
chrome_version()
chrome_read_html("http://httpbin.org/")## {xml_document}
## <html>
## [1] <head>\n<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">\n<meta http-equiv="content-type" valu ...
## [2] <body id="manpage">\n<a href="http://github.com/kennethreitz/httpbin"><img style="position: absolute; top: 0; rig ...
chrome_dump_pdf("http://httpbin.org/")chrome_shot("http://httpbin.org/")
## format width height colorspace filesize
## 1 PNG 1600 1200 sRGB 215680