MATLAB Central Newsreader - starting engopen

starting engopen

Thomas — Fri, 23 Nov 2007 16:46:44 -0500

Folks,
I need some inspiration. On my private machine (Windows XP,
MS Visual C++ Express) the following code works fine:

#include <stdio.h>
#include "engine.h"
int main()
{
Engine *ep;
if (!(ep = engOpen("\0"))) {
fprintf(stderr, "\nCan't start MATLAB engine\n");
return EXIT_FAILURE;
}
engClose(ep);
return EXIT_SUCCESS;
}

On my machine at work MATLAB doesn't start. At both
machines I have the same MATLAB version (7.5). At work I am
using Windows, too. MATLAB is an environment variable and
can start from any path. I have used "matlab \regserver".
Here's the path of MATLAB on my machine

C:\Program Files\MATLAB\R2007b\bin

and here's my exe file generated by Visual C++ (it
compiles, so no problems with the embedding of the header
or the linking)...

C:\Documents and Settings\t.mysurname\winEngine\release

Maybe there is some more explicit way to start MATLAB. Or
shall I use a *.bat file?
It also doesn't seem to work if MATLAB is already open...
Any ideas?
Thomas

Re: starting engopen

Thomas — Fri, 23 Nov 2007 17:24:56 -0500

Ok, I have done some further research and here's what's
going on:

I see that Matlab boots up
when engOpen("\0") is executed, but then Matlab immediately
quits
before execution passes to the next line. I have tried
calling both
"matlab /regserver" and "matlab /Automation" from the
Windows command
line; both call up Matlab, but then Matlab still quits when
engOpen
is called.

I have no leads to determine the cause of the problem.

Any suggestions?

Thank you,
Thomas

compare with
http://www.code-hosting.com/Matlab/1552688-engOpen---
returns-NULL-after-upgrade-to-R14-SP3-on-XP

Re: starting engopen

James Tursa — Fri, 23 Nov 2007 20:31:54 -0500

On Fri, 23 Nov 2007 17:24:56 +0000 (UTC), "Thomas "
<thomas.schmelzer.nospam@gmail.com> wrote:

>Ok, I have done some further research and here's what's
>going on:
>
>
>I see that Matlab boots up
>when engOpen("\0") is executed, but then Matlab immediately
>quits
>before execution passes to the next line. I have tried
>calling both
>"matlab /regserver" and "matlab /Automation" from the
>Windows command
>line; both call up Matlab, but then Matlab still quits when
>engOpen
>is called.
>
>I have no leads to determine the cause of the problem.
>
>Any suggestions?
>
>Thank you,
>Thomas
>
>compare with
>http://www.code-hosting.com/Matlab/1552688-engOpen---
>returns-NULL-after-upgrade-to-R14-SP3-on-XP

Here is the MATLAB doc on this:

    External Interfaces Reference
    engOpen (C)

    Start MATLAB engine session
    C Syntax

    #include "engine.h"
    Engine *engOpen(const char *startcmd);

    Arguments

    startcmd

    String to start MATLAB process. On Windows, the startcmd string
must be NULL.

So here is what I use to open the engine on Windows XP:

ep = engOpen( NULL );

i.e., I am passing the NULL pointer to engOpen. You are not passing
the NULL pointer to engOpen, you are passing a valid string, namely

"\0"

This is a string with a valid memory address containing two
characters, the null character and another null character terminator.
Not the same thing as I am doing or what MATLAB doc says.

And remember the engine opens pointed to the default startup directory
for MATLAB, which may not be the same directory as your c program. If
you need help fixing that part let me know.

James Tursa

Re: starting engopen

Thomas — Sat, 24 Nov 2007 11:15:30 -0500

James Tursa <aclassyguywithaknotac@hotmail.com> wrote in
message <cjdek3lmoblqs33mibkf45l9bud8sil65v@4ax.com>...

James,
changing from "\0" to NULL doesn't change the behaviour in
my case. I have also tried strings like "matlab" or
strings like "startMatlab" where startMatlab.bat is a file
that can start Matlab and is located in the same folder as
the *.exe file of my program.

I think the problem is better described in my second
posting where I describe that MATLAB starts but closes
after a second. I wish I would know what's going on...

Can you please help me on that issue:
> And remember the engine opens pointed to the default
startup directory
> for MATLAB, which may not be the same directory as your
c program. If
> you need help fixing that part let me know.
>

I have read the MATLAB documenation and I have wasted
several hours with this problem.

Best,
Thomas

Re: starting engopen

sfreeman — Sun, 03 Feb 2008 17:21:01 -0500

>
> Can you please help me on that issue:
> > And remember the engine opens pointed to the default
> startup directory
> > for MATLAB, which may not be the same directory as your
> c program. If
> > you need help fixing that part let me know.
> >

with C-Code in Windows this works (needs afaik windows.h):

char dir[MAX_PATH];
GetCurrentDirectory(MAX_PATH,dir); /* get pwd*/
... (insert engOpen with your error handling here) ...
engEvalString(ep, strcat("cd ",dir)); /*change to directory
first*/
... (rest usage of engine) ...

it is not vanilla, but it works :o)
Mathworks could include a few more hints with c in the
example section, I think...

Regards,

Rainer