# Matlab window issue **URL:** \ **Category:** Support\ **Created:** [July 17, 2014, 7:15pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552 "2014-07-17T19:15:42Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 17, 2014, 7:15pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/1 "2014-07-17T19:15:42Z")
Hi Chris, I’m learning how to use the Matlab window. One small question, and a problem: - What does “process {x} events” mean? Why is it 0 sometimes, and 1 other times? - I’ve written an m-file that plots some data every time it’s called. From your example, the way this gets called is that “sync” is set from 1 to 0. My MWorks program cycles through blocks of trials, setting sync = 1 at the start of the block, 0 at the end, then back to 1 immediately. The data from the first block gets plotted, but not for successive blocks. Stopping and starting the program doesn’t fix the problem. In fact, if I try to unload the program after the m-file has been called, the client stops responding and I have to force quit. Would you mind helping me figure out what’s going wrong? Thanks, Evan ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 17, 2014, 7:37pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/2 "2014-07-17T19:37:16Z")
Hi Evan, > What does “process {x} events” mean? Why is it 0 sometimes, and 1 other times? If “Collecting Data” is checked but “Process X events” is not, then the MATLAB bridge will collect the selected events but will _not_ invoke your script. If you subsequently check “Process events”, the collected events will be sent to your script at that time. > The data from the first block gets plotted, but not for successive blocks. Stopping and starting the program doesn’t fix the problem. In fact, if I try to unload the program after the m-file has been called, the client stops responding and I have to force quit. I think this is a bug. I see it with MATLAB R2014a, but not with R2011a. Let me dig in a little further and see what’s going on. Thanks, Chris ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 18, 2014, 2:07pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/3 "2014-07-18T14:07:21Z")
Hi Evan, It looks like the client freeze is related to [this issue](https://mworks.discourse.group/discussions/problems/115). It appears that under MATLAB R2014a, the MATLAB engine API (specifically the [engGetVariable](http://www.mathworks.com/help/matlab/apiref/enggetvariable.html) function) gets stuck when the variable value is an int64 array. The only feedback we get is a rather unhelpful message sent to the console: ``` {Error using save Can't write file stdio. } Error writing to output stream. ``` I assume this is a bug, not a design choice. The fix is to ensure that your MATLAB script returns a double array. I’ve attached an updated matlab\_window\_demo.m and will also post it to the tutorial. Cheers, Chris ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 18, 2014, 2:07pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/4 "2014-07-18T14:07:21Z")
Attachment: [matlab\_window\_demo.m](https://mworks.discourse.group/uploads/short-url/pIUaSrqUGdBZo1dct3GqHCX2sUG.m) (499 Bytes) ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 18, 2014, 5:33pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/5 "2014-07-18T17:33:17Z")
Hi Chris, Thanks for figuring that out. I was using a struct (of doubles), but either way using the double array fixed the problem. I guess it would be nice to be able to use other data types (like structs), but this works so that would be a low priority item if anything. Maybe it would help to submit a bug report to Mathworks? Also, how did you know the problem was in the return value from the matlab script? Just that console message? - Evan ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 18, 2014, 8:10pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/6 "2014-07-18T20:10:55Z")
> Maybe it would help to submit a bug report to Mathworks? Yeah, that’s probably a good idea. > Also, how did you know the problem was in the return value from the matlab script? Just that console message? I ran MWClient in the Xcode debugger and saw that it (1) hung at engGetVariable and (2) produced that console message. Feeding the console message in to Google led me to [this thread](http://www.mathworks.com/matlabcentral/newsreader/view_thread/335923), which suggested that the data type of the variable was the problem. Actually, I fully expected this to be an MWorks bug, so I was both pleased and surprised to discover that it wasn’t. Chris ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 18, 2014, 12:28pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/7 "2014-09-18T12:28:38Z")
Just an update - I finally submitted a ticket to Matlab about adding support for other data types in the engGetVariable function. ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 22, 2014, 1:09am UTC](https://mworks.discourse.group/t/matlab-window-issue/552/8 "2014-09-22T01:09:16Z")
Hi Chris, I heard back from The Mathworks. They passed along an example program. From the rep: > I have created a sample C program file ‘demo.c’ which demonstrates the usage of ‘engGetVariable’ method to get the ‘struct’ and ‘cell array’ data structures from that MATLAB environment to the C environment. I have also added the appropriate comments wherever necessary inside the code. > In order to compile demo.c program, please use following command at MATLAB command line: > `mex -client engine demo.c` > This will generate an ‘exe’ file. Please execute this file using windows command prompt to see the output of ‘printf’ statements inside the code. I don’t have anything waiting on this functionality. Just wanted to add the update. Evan ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 22, 2014, 1:09am UTC](https://mworks.discourse.group/t/matlab-window-issue/552/9 "2014-09-22T01:09:16Z")
Attachment: [demo.c](https://mworks.discourse.group/uploads/short-url/aS0DMM54kwZDFsLoLKj17lTAFER.c) (1.94 KB) ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 24, 2014, 3:01pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/10 "2014-09-24T15:01:25Z")
Hi Evan, The example program demonstrates the same bug: ``` >> mex -client engine demo.c Building with 'Xcode with Clang'. MEX completed successfully. >> quit $ DYLD_LIBRARY_PATH=/Applications/MATLAB_R2014a.app/bin/maci64 ./demo Creating structure 'sampleStructure' Retrieving structure 'sampleStructure' Error using save Can't write file stdio. ``` And there it hangs. It sounds like the MathWorks guy tested his example on Windows. Maybe you should tell him to try it on a Mac. Thanks, Chris ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 25, 2014, 8:00pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/11 "2014-09-25T20:00:31Z")
Relaying from Mathworks: > I tried to run ‘demo.c’ program on Mac operating system. I was successfully able to \>run it on Mac OS X 10.9.2 from system terminal. Following are the steps which I \>followed for compiling and running this program: > > 1. At the beginning, I made sure that the ‘PATH’ environment variable includes /bin > path. > If it is not present in your case, then you can use the following command to include that path: > setenv PATH ‘/bin’:$PATH > > 2. I then executed following commands in order to set the environment variable > ‘DYLD\_LIBRARY\_PATH’ properly. > > 3. I compiled demo.c program from MATLAB command line using following command: > mex -client engine demo.c > 1. I ran demo program from the same system terminal as below ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 26, 2014, 2:36pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/12 "2014-09-26T14:36:52Z")
Hi Evan, I still see the bug: ``` $ PATH=/Applications/MATLAB_R2014a.app/bin:$PATH DYLD_LIBRARY_PATH=/Applications/MATLAB_R2014a.app/bin/maci64:/Applications/MATLAB_R2014a.app/sys/os/maci64 ./demo Creating structure 'sampleStructure' Retrieving structure 'sampleStructure' Error using save Can't write file stdio. ``` I tried it on two machines, one running OS X 10.9.5, the other 10.8.5, and I got the same result both times. If there a way for me to get in touch with this person directly? Or should I just open another bug report? Thanks, Chris ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [September 27, 2014, 12:39pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/13 "2014-09-27T12:39:11Z")
Hi Chris, Apparently this bug is specific to Mac/2014a, and will be fixed in the 2014b release. Not sure why Mathworks didn’t catch that initially; the OS/release version was included in my original service request. Sorry about the time waste on this. - Evan ---
**Author:** ![cstawarz](https://yyz1.discourse-cdn.com/flex031/user_avatar/mworks.discourse.group/cstawarz/32/3_2.png) [@cstawarz](https://mworks.discourse.group/u/cstawarz)\ **Post date:** [July 19, 2022, 10:57pm UTC](https://mworks.discourse.group/t/matlab-window-issue/552/14 "2022-07-19T22:57:08Z")