What it is

Sometimes you don't have the time to wait.

Although most Lisps have a mechanism to write code that says "do this for 5 seconds and give up if you're not done", they didn't agree on exactly what that mechanism should look like. Trivial-timeout steps into the gap with a platform independent syntax for timeouts. You use it like this: 

(with-timeout (duration)  
  (run-some-long-running-code))

If duration (a time in seconds) is exceeded, then a timeout-error will be signaled. A more idiomatic example would probably be: 

(handler-case  
  (with-timeout (60)  
    (make-microwave-popcorn))  
  (timeout-error (c)  
    (declare (ignore c))  
    (print "I wanted to make popcorn, but who has the time these days")))

Here's the full skinny:

with-timeout (seconds) &body body
macro

Execute body for no more than seconds time.

If seconds is exceeded, then a timeout-error will be signaled.

If seconds is nil, then the body will be run normally until it completes or is interrupted.

timeout-error
condition
An error signaled when the duration specified in the with-timeout is exceeded.

Mailing Lists

Where is it

A darcs repository is available. The darcs command is: 

darcs get http://common-lisp.net/project/trivial-timeout/

trivial-timeout is also ASDF installable. Its CLiki home is right where you'd expect.

There's also a handy gzipped tar file.

What is happening

10 Sept 2008 - Separated trivial-timeout from lift and trivial-shell. There was much rejoicing.