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Simple library for asynchronous processing in Emacs
Emacs Lisp
Branch: master

License GPL 3 MELPA MELPA Stable


async.el is a module for doing asynchronous processing in Emacs.


Add to your .emacs.el:

(autoload 'dired-async-mode "dired-async.el" nil t)
(dired-async-mode 1)

This will allow you to run asynchronously the dired commands for copying, renaming and symlinking. If you are a helm user, this will allow you to copy, rename etc... asynchronously from helm. Note that with helm you can disable this by running the copy, rename etc... commands with a prefix argument.

If you don't want to make dired/helm asynchronous disable it with dired-async-mode.


The interface is intended to be very easy to use:



Execute START-FUNC (often a lambda) in a subordinate Emacs process. When done, the return value is passed to FINISH-FUNC. Example:

   ;; What to do in the child process
   (lambda ()
     (message "This is a test")
     (sleep-for 3)

   ;; What to do when it finishes
   (lambda (result)
     (message "Async process done, result should be 222: %s" result)))

If FINISH-FUNC is nil or missing, a future is returned that can be inspected using async-get, blocking until the value is ready. Example:

(let ((proc (async-start
               ;; What to do in the child process
               (lambda ()
                 (message "This is a test")
                 (sleep-for 3)

    (message "I'm going to do some work here") ;; ....

    (message "Waiting on async process, result should be 222: %s"
             (async-get proc)))

If you don't want to use a callback, and you don't care about any return value from the child process, pass the 'ignore symbol as the second argument (if you don't, and never call async-get, it will leave *emacs* process buffers hanging around):

 (lambda ()
   (delete-file "a remote file on a slow link" nil))

Note: Even when FINISH-FUNC is present, a future is still returned except that it yields no value (since the value is passed to FINISH-FUNC). Calling async-get on such a future always returns nil. It can still be useful, however, as an argument to async-ready or async-wait.



Start the executable PROGRAM asynchronously. See async-start. PROGRAM is passed PROGRAM-ARGS, calling FINISH-FUNC with the process object when done. If FINISH-FUNC is nil, the future object will return the process object when the program is finished. Set DEFAULT-DIRECTORY to change PROGRAM's current working directory.


async-get FUTURE

Get the value from an asynchronously called function when it is ready. FUTURE is returned by async-start or async-start-process when its FINISH-FUNC is nil.


async-ready FUTURE

Query a FUTURE to see if its function's value is ready -- i.e., if no blocking would result from a call to async-get on that FUTURE.


async-wait FUTURE

Wait for FUTURE to become ready.


async-inject-variables INCLUDE-REGEXP &optional PREDICATE EXCLUDE-REGEXP

Return a setq form that replicates part of the calling environment. It sets the value for every variable matching INCLUDE-REGEXP and also PREDICATE. It will not perform injection for any variable matching EXCLUDE-REGEXP (if present). It is intended to be used as follows:

   `(lambda ()
      (require 'smtpmail)
        (insert ,(buffer-substring-no-properties (point-min) (point-max)))
        ;; Pass in the variable environment for smtpmail
        ,(async-inject-variables "\\`\\(smtpmail\\|\\(user-\\)?mail\\)-")
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