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4 Send URL: Opening a Web Browser

 (require net/sendurl)
Provides send-url for opening a URL in the user’s chosen web browser.

See also browser/external, which requires scheme/gui, but can prompt the user for a browser if no browser preference is set.

(send-url str    
  [separate-window?    
  #:escape escape?]) → void?
  str : string?
  separate-window? : any/c = #t
  escape? : any/c = #t
Opens str, which represents a URL, in a platform-specific manner. For some platforms and configurations, the separate-window? parameter determines if the browser creates a new window to display the URL or not.

Under Windows, send-url normally uses shell-execute to launch a browser. (If the URL appears to contain a fragment, it may use an intermediate redirecting file due to a bug in IE7.)

Under Mac OS X, send-url runs osascript to start the user’s chosen browser.

Under Unix, send-url uses a user-preference, or when none is set, it will look for a known browser. See the description of external-browser for details.

The url string is usually escaped to avoid dangerous shell characters (quotations, dollar signs, backslashes, and non-ASCII). Note that it is a good idea to encode URLs before passing them to this function.

On all platforms, external-browser parameter can be set to a procedure to override the above behavior – the procedure will be called with the url string.

(send-url/file path    
  [separate-window?    
  #:fragment fragment    
  #:query query]) → void?
  path : path-string?
  separate-window? : any/c = #t
  fragment : (or/c string? false/c) = #f
  query : (or/c string? false/c) = #f
Similar to send-url, but accepts a path to a file to be displayed by the browser. Use this function when you want to display a local file: it takes care of the peculiarities of constructing the correct file:// URL, and uses send-url to display the file. If you need to use an anchor fragment or a query string, use the corresponding keyword arguments.

(send-url/contents contents    
  [separate-window?    
  #:fragment fragment    
  #:query query    
  #:delete-at seconds]) → void?
  contents : string?
  separate-window? : any/c = #t
  fragment : (or/c string? false/c) = #f
  query : (or/c string? false/c) = #f
  seconds : (or/c number? false/c) = #f
Similar to send-url/file, but it consumes the contents of a page to show, and displayes it from a temporary file.

If delete-at is a number, the temporary file is removed after this many seconds. The deletion happens in a thread, so if mzscheme exits before that it will not happen – when this function is called it scans old generated files (this happens randomly, not on every call) and removes them to avoid cluttering the temporary directory. If delete-at is #f, no delayed deletion happens, but old temporary files are still deleted as described above.

(external-browser) → browser-preference?
(external-browser cmd) → void?
  cmd : browser-preference?
A parameter that can hold a procedure to override how a browser is started, or #f to use the default platform-dependent command.

Under Unix, the command that is used depends on the 'external-browser preference. If the preference is unset, send-url uses the first of the browsers from unix-browser-list for which the executable is found. Otherwise, the preference should hold a symbol indicating a known browser (from the unix-browser-list), or it a pair of a prefix and a suffix string that are concatenated around the url string to make up a shell command to run. In addition, the external-browser paremeter can be set to one of these values, and send-url will use it instead of the preference value.

Note that the URL is encoded to make it work inside shell double-quotes: URLs can still hold characters like #, ?, and &, so if the external-browser is set to a pair of prefix/suffix strings, they should use double quotes around the url.

If the preferred or default browser can’t be launched, send-url fails. See get-preference and put-preferences for details on setting preferences.

(browser-preference? a) → boolean?
  a : any/c
Returns #t if v is a valid browser preference, #f otherwise. See external-browser for more information.

unix-browser-list : (listof symbol?)
A list of symbols representing Unix executable names that may be tried in order by send-url. The send-url function internally includes information on how to launch each executable with a URL.

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