132 lines
4.0 KiB
Markdown
132 lines
4.0 KiB
Markdown
# About chromedp [![Build Status][1]][2] [![Coverage Status][3]][4]
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Package chromedp is a faster, simpler way to drive browsers in Go using the
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[Chrome Debugging Protocol][5] (for Chrome, Edge, Safari, etc) without external
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dependencies (ie, Selenium, PhantomJS, etc).
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**NOTE:** chromedp's API is currently unstable, and may change at a moments
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notice. There are likely extremely bad bugs lurking in this code. **CAVEAT USER**.
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## Installing
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Install in the usual way:
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```sh
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go get -u github.com/chromedp/chromedp
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```
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## Using
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Below is a simple Google search performed using chromedp (taken from
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[examples/simple][6]):
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This example shows logic for a simple search for a known website, clicking on
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the right link, and then taking a screenshot of a specific element on the
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loaded page and saving that to a local file on disk.
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```go
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// Command simple is a chromedp example demonstrating how to do a simple google
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// search.
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package main
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import (
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"context"
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"fmt"
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"io/ioutil"
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"log"
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"time"
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"github.com/chromedp/cdproto/cdp"
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"github.com/chromedp/chromedp"
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)
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func main() {
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var err error
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// create context
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ctxt, cancel := context.WithCancel(context.Background())
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defer cancel()
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// create chrome instance
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c, err := chromedp.New(ctxt, chromedp.WithLog(log.Printf))
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if err != nil {
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log.Fatal(err)
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}
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// run task list
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var site, res string
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err = c.Run(ctxt, googleSearch("site:brank.as", "Home", &site, &res))
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if err != nil {
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log.Fatal(err)
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}
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// shutdown chrome
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err = c.Shutdown(ctxt)
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if err != nil {
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log.Fatal(err)
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}
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// wait for chrome to finish
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err = c.Wait()
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if err != nil {
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log.Fatal(err)
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}
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log.Printf("saved screenshot from search result listing `%s` (%s)", res, site)
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}
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func googleSearch(q, text string, site, res *string) chromedp.Tasks {
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var buf []byte
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sel := fmt.Sprintf(`//a[text()[contains(., '%s')]]`, text)
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return chromedp.Tasks{
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chromedp.Navigate(`https://www.google.com`),
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chromedp.WaitVisible(`#hplogo`, chromedp.ByID),
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chromedp.SendKeys(`#lst-ib`, q+"\n", chromedp.ByID),
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chromedp.WaitVisible(`#res`, chromedp.ByID),
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chromedp.Text(sel, res),
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chromedp.Click(sel),
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chromedp.WaitNotVisible(`.preloader-content`, chromedp.ByQuery),
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chromedp.WaitVisible(`a[href*="twitter"]`, chromedp.ByQuery),
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chromedp.Location(site),
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chromedp.ScrollIntoView(`.banner-section.third-section`, chromedp.ByQuery),
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chromedp.Sleep(2 * time.Second), // wait for animation to finish
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chromedp.Screenshot(`.banner-section.third-section`, &buf, chromedp.ByQuery),
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chromedp.ActionFunc(func(context.Context, cdp.Executor) error {
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return ioutil.WriteFile("screenshot.png", buf, 0644)
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}),
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}
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}
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```
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Please see the [examples][6] project for more examples. Please refer to the
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[GoDoc API listing][7] for a summary of the API and Actions.
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## Resources
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* [chromedp: A New Way to Drive the Web][8] - GopherCon SG 2017 talk
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* [Chrome DevTools Protocol][5] - Chrome Debugging Protocol Domain documentation
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* [chromedp examples][6] - various `chromedp` examples
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* [`github.com/chromedp/cdproto`][9] - GoDoc listing for the CDP domains used by `chromedp`
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* [`github.com/chromedp/cdproto-gen`][10] - tool used to generate `cdproto`
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* [`github.com/chromedp/chromedp-proxy`][11] - a simple CDP proxy for logging/debugging CDP clients and browser instances
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## TODO
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* Move timeouts to context (defaults)
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* Implement more query selector options (allow over riding context timeouts)
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* Contextual actions for "dry run" (or via an accumulator?)
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* Network loader / manager
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* Profiler
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[1]: https://travis-ci.org/chromedp/chromedp.svg
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[2]: https://travis-ci.org/chromedp/chromedp
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[3]: https://coveralls.io/repos/chromedp/chromedp/badge.svg?branch=master&service=github
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[4]: https://coveralls.io/github/chromedp/chromedp?branch=master
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[5]: https://chromedevtools.github.io/devtools-protocol/
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[6]: https://github.com/chromedp/examples
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[7]: https://godoc.org/github.com/chromedp/chromedp
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[8]: https://www.youtube.com/watch?v=_7pWCg94sKw
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[9]: https://godoc.org/github.com/chromedp/cdproto
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[10]: https://github.com/chromedp/cdproto-gen
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[11]: https://github.com/chromedp/chromedp-proxy
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