Section: FreeMat Threads
threadvalue function retrieves the values returned
by the function specified in the threadnew call. The
syntax for its use is
[arg1,arg2,...,argN] = threadvalue(handle)
where handle is the value returned by a threadnew call.
Note that there are issues with nargout. See the examples
section of threadnew for details on how to work around this
limitation. Because the function you have spawned with threadnew
may still be executing, threadvalue must first threadwait
for the function to complete before retrieving the output values.
This wait may take an arbitrarily long time if the thread function
is caught in an infinite loop. Hence, you can also specify
a timeout parameter to threadvalue as
[arg1,arg2,...,argN] = threadvalue(handle,timeout)
where the timeout is specified in milliseconds. If the
wait times out, an error is raised (that can be caught with a
try and catch block.
In either case, if the thread function itself caused an error
and ceased execution abruptly, then calling threadvalue will
cause that function to raise an error, allowing you to retrieve
the error that was caused and correct it. See the examples section
for more information.
system call in a thread.
--> a = threadnew; % Create the thread --> threadstart(a,'system',1,'ls -lrt /'); % Start the thread --> b = rand(100) and(100,1); % Solve some equations simultaneously --> c = threadvalue(a); % Retrieve the file list --> size(c) % It is large! ans = 22 1 --> threadfree(a); --> quit
In this example, we force the threaded function to cause an
exception (by calling the error function as the thread
function). When we call threadvalue, we get an error, instead
of the return value of the function
--> a = threadnew a = 3 --> threadstart(a,'error',0,'Hello world!'); % Will immediately stop due to error --> c = threadvalue(a) % The error comes to us Error: Thread: Hello world! --> threadfree(a) --> quit
Note that the error has the text Thread: prepended to the message
to help you identify that this was an error in a different thread.