async.el is a module for doing asynchronous processing in Emacs.
Some async applications are provided as well with this package:
Add to your
(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
Debian and Ubuntu
Users of Debian 9 or later or Ubuntu 16.04 or later may simply
apt-get install elpa-async.
Enable asynchronous compilation of your (M)elpa packages
By default emacs package.el compile packages in its running emacs session. This is not a problem when installing a new package (which is not actually loaded in current emacs) but it may create errors and bad compilation when upgrading a package (old version of package is already loaded and running in current emacs). You can remedy to this by allowing async to compile your packages asynchronously, (helm and magit actually do this by default, so if you are using these packages they will compile asynchronously) to do this, add to your init file:
You can control which packages will compile async with
Set it to
'(all) to be sure you will compile all packages asynchronously.
The interface is intended to be very easy to use:
async-start START-FUNC FINISH-FUNC
Execute START-FUNC (often a lambda) in a subordinate Emacs process. When done, the return value is passed to FINISH-FUNC. Example:
(async-start ;; What to do in the child process (lambda () (message "This is a test") (sleep-for 3) 222) ;; 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
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) 222)))) (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
(async-start (lambda () (delete-file "a remote file on a slow link" nil)) 'ignore)
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-start-process NAME PROGRAM FINISH-FUNC &rest PROGRAM-ARGS
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
Get the value from an asynchronously called function when it is ready. FUTURE is
async-start-process when its FINISH-FUNC is
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.
Wait for FUTURE to become ready.
async-inject-variables INCLUDE-REGEXP &optional PREDICATE EXCLUDE-REGEXP
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:
(async-start `(lambda () (require 'smtpmail) (with-temp-buffer (insert ,(buffer-substring-no-properties (point-min) (point-max))) ;; Pass in the variable environment for smtpmail ,(async-inject-variables "\\`\\(smtpmail\\|\\(user-\\)?mail\\)-") (smtpmail-send-it))) 'ignore)
async-let BINDINGS &rest FORMS
Allow to establish let bindings asynchronously.
Each value of binding can refer to the symbols already bound in BINDINGS (like
FORMS are executed once BINDINGS have been evaluated, but without blocking emacs.
(async-let ((x "hello") (y "world")) (message "%s %s" x y)) (async-let ((x (* 5 2)) (y (+ x 4)) (z (+ x y))) (message "%d + %d = %d" x y z))
Note that if you bind something to nil and set it afterward in body, the evaluation of this binding will NOT be asynchronous, but will happen in you current emacs, blocking it if the evaluation of this value is sufficiently important, e.g:
(async-let ((x "hello") (y "world") z) (setq z (+ 1 2)) ;; Huge calculation of Z will block emacs. (message "%s %s %d" x y z))
IOW if the calculation of Z is huge and you want it asynchronous evaluate it in BINDINGS but not in FORMS.