What is the difference between a system call from Matlab (using system()) and a command in a cmd terminal?

Hi,

I've got Matlab2016b installed on a Windows 7 Professional 64 bits machine.

I've got a specific program that behaves differently when calling it in Matlab using the system() command (or the dos() command, effect is the same) and running the same command from a cmd terminal of Windows. I make sure that the current path of Matlab is the same as the current path of the cmd when I do this function call. The command includes several command line options and looks like this:

In Matlab:

>> disp(pwd)
D:\location
>> system('"C:\somewhere\prog.exe" 0 1 0')

ans =

      -1.073741512000000e+09

In the cmd terminal:

D:\location> "C:\somewhere\prog.exe" 0 1 0
<... lots of output ...>

D:\location> echo %errorlevel%
0

The %errorlevel% contains the exit code, which is also the return value of the system() call in Matlab. The behavior in the cmd terminal is correct, it generates the results I need.

So what could be going on here? This is not general behavior, but for this specific program. Of course I'm also in contact with the developers of that program, but I would like to know what the difference is between these two ways of running a program.

[Jan]

 The %errorlevel% contains the exit code, which is also the return
 value of the system() call in Matlab

Is it? -1.073741512000000e+09 does not seem to be 0.

What do you get if you catch the outputs?

[status, out] = system('"C:\somewhere\prog.exe" 0 1 0')

What exactly are you missing?

Does the environment contain different settings?

[status, out] = system('pwd & set')

and run "pwd" and "set" in the command window also to compare.

[Guillaume]

Arjan Lampe's comment mistakenly posted as an answer moved here (please use comments unless answering the question):

Is it? -1.073741512000000e+09 does not seem to be 0.

That's exactly the problem :) I've no clue why this would be the return value.

What do you get if you catch the outputs?

out is empty

Does the environment contain different settings?

Ok, that's a good point. There is indeed a difference in the environment. And when I make them equal, I get the same error in the cmd.

It has to do with this library: libiomp5md.dll

In the matlab environment this exists:

__KMP_REGISTERED_LIB_6028=000007FEE9DE7954-cafed93d-libiomp5md.dll

Can this be undone? Or why is it there in the first place?

[Arjan Lampe]

Ok, this has been solved. It had to do with an addition to the path variable. Undoing that solves the problem.

Answer 1

[Arjan Lampe]

It turned out that when using system() or dos() an extra path is included in the path variable. In my case it is this path: C:\Program Files\Legacy Apps\MATLAB\R2016b\bin\win64

This path included a library called libiomp5md.dll which caused a conflict with the program that I was trying to run. Removing this path from the path variable again solved the issue.

[kaiming guo]

Still don't get it worked. "Removing this path from the path variable". in your case, is it will be removing path: C:\Program Files\Legacy Apps\MATLAB\R2016b\bin\win64 from Environment variable in windows system? or there will be some other ways to get going. Appreciate your helps.

[Arjan Lampe]

If in the Matlab prompt you do (assuming windows)

 >> [out, txt] = system('set')
 >> fid = fopen('MatlabEnv.txt', 'w')
 >> fprintf(fid,'%s',txt)
 >> close(fid)

And then go to a cmd prompt and do this:

 C:\somewhere> set > cmdEnv.txt

Now you have two text files which contain the environment in which commands are executed. If you compare them, you see the difference between them. There is always a variable called 'Path' which contains search paths for, among many other things, dll files. The format is something like:

 Path=<dir1>;<dir2>;<dir3>

for example:

 Path=C:\Program Files\bin;C:\Program Files (x86)\Common Files;D:\bla

Now, for Matlab this path contained a directory called C:\Program Files\Legacy Apps\MATLAB\R2016b\bin\win64, in the cmd prompt this was not the case. So I ran the matlab command like this to avoid problems:

 >> fid = fopen('myBatchFile.bat','w')
 >> fprintf(fid,'%s\n','set path=%path:C:\Program Files\Legacy Apps\MATLAB\R2016b\bin\win64;=%');
 >> fprintf(fid,'%s\n','someCommand.exe 0 1 0')
 >> fclose(fid)
 >> system('myBatchFile.bat')

This solved the problem in my case.

[kaiming guo]

Thanks a lot! Now it is working again. Appreciate your time and patient!

Answer 2

[Swati Lodha]

A system call from using MATLAB using system(): 

>> status = system(command)

calls the operating system to execute the specified command. The operation waits for the command to finish execution before returning the exit status of the command to the status variable. The function starts a new cmd/shell process, executes command, exits the process, and returns to the MATLAB® process. Updates to the system environment made by command are not visible to MATLAB.

Whereas, The operating system command is specified as a string or a character vector like "dir", "ls" etc. The command executes in a system shell, which might not be the shell from which you started MATLAB.

Answer 3

[kaiming guo]

I have exactly same issue. Is it due to environment setting? I wish to get some hints on how to set up the environment for this issue.

[Arjan Lampe]

I've added the answer.

[kaiming guo]

Thanks for your answers. Really appreciated! Hopefully, you have seen my comment. I may need more descriptions.

Answer 4

[Philipp Krauter]

There is a simple workaround for the problem. Newer versions of Matlab are adding a folder to the Path environmental variable each time, system() or dos() function are called. For me, removing this new path by calling

system('set path=%path:C:\Program Files\MATLAB\R2018b\bin\win64;=% & myprog.exe');

instead of

system('myprog.exe');

solves the problem.

Please note, that the folder to be removed from the environmental variable can differ. It can be read out using

system('path');