Info Catalog url: URI Parsing url: Top url: Supported URL Types

url: Retrieving URLs

 
 3 Retrieving URLs
 *****************
 
 The ‘url’ library defines the following three functions for retrieving
 the data specified by a URL.  The actual retrieval protocol depends on
 the URL’s URI scheme, and is performed by lower-level scheme-specific
 functions.  (Those lower-level functions are not documented here, and
 generally should not be called directly.)
 
    In each of these functions, the URL argument can be either a string
 or a parsed URL structure.  If it is a string, that string is passed
 through ‘url-encode-url’ before using it, to ensure that it is properly
 URI-encoded (URI Encoding).
 
  -- Function: url-retrieve-synchronously url silent no-cookies
      This function synchronously retrieves the data specified by URL,
      and returns a buffer containing the data.  The return value is
      ‘nil’ if there is no data associated with the URL (as is the case
      for ‘dired’, ‘info’, and ‘mailto’ URLs).
 
      If the optional argument SILENT is non-‘nil’, progress messages are
      suppressed.  If the optional argument NO-COOKIES is non-‘nil’,
      cookies are not stored or sent.
 
  -- Function: url-retrieve url callback &optional cbargs silent
           no-cookies
      This function retrieves URL asynchronously, calling the function
      CALLBACK when the object has been completely retrieved.  The return
      value is the buffer into which the data will be inserted, or ‘nil’
      if the process has already completed.
 
      The callback function is called this way:
 
           (apply CALLBACK STATUS CBARGS)
 
      where STATUS is a plist representing what happened during the
      retrieval, with most recent events first, or an empty list if no
      events have occurred.  Each pair in the plist is one of:
 
      ‘(:redirect REDIRECTED-TO)’
           This means that the request was redirected to the URL
           REDIRECTED-TO.
 
      ‘(:error (ERROR-SYMBOL . DATA))’
           This means that an error occurred.  If so desired, the error
           can be signaled with ‘(signal ERROR-SYMBOL DATA)’.
 
      When the callback function is called, the current buffer is the one
      containing the retrieved data (if any).  The buffer also contains
      any MIME headers associated with the data retrieval.
 
      If the optional argument SILENT is non-‘nil’, progress messages are
      suppressed.  If the optional argument NO-COOKIES is non-‘nil’,
      cookies are not stored or sent.
 
  -- Function: url-queue-retrieve url callback &optional cbargs silent
           no-cookies
      This function acts like ‘url-retrieve’, but with limits on the
      number of concurrently-running network processes.  The option
      ‘url-queue-parallel-processes’ controls the number of concurrent
      processes, and the option ‘url-queue-timeout’ sets a timeout in
      seconds.
 
      To use this function, you must ‘(require 'url-queue)’.
 
  -- User Option: url-queue-parallel-processes
      The value of this option is an integer specifying the maximum
      number of concurrent ‘url-queue-retrieve’ network processes.  If
      the number of ‘url-queue-retrieve’ calls is larger than this
      number, later ones are queued until earlier ones are finished.
 
  -- User Option: url-queue-timeout
      The value of this option is a number specifying the maximum
      lifetime of a ‘url-queue-retrieve’ network process, once it is
      started.  If a process is not finished by then, it is killed and
      removed from the queue.
 

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