Run exe with an input file and close upon process exit

Hi,

I am creating a GUI where the user is to input parameters, MATLAB then creates an input file (exp.in) that is to be read into an exe. Once the cfd computations have completed, I would like the exe to close itself (if it is successful). I have the following created using similar queries by others however do not know how to go about passing the exe an input file.

proc = System.Diagnostics.Process(); 
proc.StartInfo.FileName = 'P:\path...cfd.exe';
%proc.StartInfo.Arguments = 'P:\path...exp.in';
proc.StartInfo.UseShellExecute = false;
proc.StartInfo.RedirectStandardInput = true;
proc.Start();

StreamWriter = proc.StandardInput;

    sIn.AutoFlush = true;
    sIn.write("dir P:\path...exp.in") 
    sIn.write("exit")  

    sIn.Close() 

if isempty(proc)
  error('Failed to launch process');
end
while true
  if proc.HasExited
      fprintf('\nProcess exited with status %d\n', proc.ExitCode);
      break
  end
  fprintf('.');
  pause(1.0);
end

Is there a way to pass on an input file for the exe to use. I have tried to use arguments but it doesn't work. Research suggests controlling process input via streamwriter.

I can use the system command to do so but then don't know how to close the exe once it finishes (have used taskkill to no avail; it closes before the process finishes).

Thanks in advance!

[OCDER]

Does the exe file have the ability to take an input like this?

system('cfd.exe -i inputfile.in')

Or must you actively put in the inputs after cfd.exe is opened up?

>> system('cfd.exe')
  cfd] -i inputfile.in
  cfd] exit
>>

[Muhammad Munib]

Yes I can run the exe in a more conventional way through the system command.

status = system('cfd.exe < inputfile.in &');
  if isempty(status)
  error('Failed to launch process');
end
while true
  if status.HasExited
      fprintf('\nProcess exited with status %d\n', status.ExitCode);
      break
  end
  fprintf(',');
  pause(1.0);
end

Matlab needs to wait for the exe to finish computing before I would like it to close the window and return to the GUI.

With the above I get the error 'Struct contents reference from a non-struct array object.'

How could I go about writing a routine that closes the exe once it finishes its operations?

Thanks.

[Guillaume]

"in a more conventional way"

Not that conventional. There's a big difference between:

C:\> cfd.exe -i inputfile.in

which pass the name of a file to the executable and leave it up to the executable to read the file

and

C:\> cfd.exe < inputfile.in &

which tells the command prompt to read the inputfile and redirect its content to the executable (which would normally take its input from the keyboard). No argument is actually passed to the executable.

By the way, I'm not sure what that final & is by the way, as far as I know it's not legal or has no effect on its own.

As far as I can tell, the .Net code you show replicate that streaming process so if there's a problem you need to clarify what it actually is. Perhaps, what you write to the input stream is not correct.

As for, "With the above I get the error 'Struct contents reference from a non-struct array object.'". Of course, as documented status is numeric, not a structure. I've no idea where you picked up

if status.HasExited

it's not going to work since as said status is numeric (either 0 or 1) and additionally, does not get updated once you've received its value.

Anyway, the way to pass arguments to your executable and the way to terminate it once it's done what you need is going to depend entirely on the way that executable is designed. Hence you need to read its documentation and explain to us how that works, or if its documentation is available publicly give us a link.

[Muhammad Munib]

Sorry I meant that most of the answers given along with documentation use

    system(cfd.exe < inputfile.in &')

With the &, it runs in its own command window, as I would like it to; without, it runs in the Matlab command window which I don't want. User should be able to see the computations and wait for them to complete.

The exe normally takes its input from the keyboard as you have stated and with '<' it accepts values sequentially. Beyond that it was written in Fortran, I would not know how it works, sorry. I've just been given the exe and am trying to create a GUI around it so users have something prettier to use than the command window as input.

The .Net code is from a similar query in Matlab Answers. I have tried to pass it arguments using

   proc.StartInfo.Arguments =  'C:\inputFile.in';

to no avail. The rest of the code, as written in the original post works as I would like. So apart from the fact that it doesn't seem to read arguments (which may explain why with '-i' doesn't read the input, I think, I may be wrong) or I can't give it an input file to read using the stream writer, it closes after I manually enter inputs upon

    if proc.HasExited

once the computations have finished.

Could I use

task = 'cfd.exe < inputfile.in'
[status, result] = system('cfd.exe < inputfile.in &');

and then write a while loop to identify when task has finished or would I have to gets its process ID.

Thanks. Appreciate any help.

Answer 1

[Guillaume]

As I said in my comment, cfd.exe < inputfile.in does not pass any input argument to the executable. It's a completely different mechanism, and proc.StartInfo.Arguments = 'C:\inputFile.in'; is not equivalent to that at all. The .Net equivalent would be

proc.Start;
streamreader = System.IO.StreamReader('C:\inputfile.in');
proc.StandardInput.Write(streamreader.ReadToEnd);

With regards to &, I was too focused on the windows side and forgot that it's a matlab argument to mean that system should return immediately without waiting for the process to finish. So, if you want matlab to continue only when the process has finished then don't include that final &.

As to killing the process, if I understood correctly, you shouldn't have to do that as your program accepts a quit command that will tells it to terminate. It's a lot cleaner than killing it.

[Muhammad Munib]

The .Net code you have written almost works so thank you. It runs the first time (and closes itself as you have mentioned) but the second time when a user changes any one of the inputs it fails with:

Error using fprintf
  Invalid file identifier. Use fopen to generate a valid file identifier.
Error in Attempt1>Run_exe_Callback (line 399)
fprintf(fileID,'%6.2d\r\n',A);

The fprintf and fopen are used to create the input file in the first place (6 numerical values each on a new line). Everytime I open Matlab again, it will work the first time but not again when I click run in the GUI. Seems the input file is still being used/written to. The program cannot write a new file replacing the existing and pass that to the exe.

The fopen uses a w+ permission, have also tried a w permission. I am working in the correct directory. Do I need to include

    proc.StandardInput.Close()

or something so stop the input file being used so that when the user wants to change input (for the next simulation) the contents of the file can be rewritten and used.

I cannot delete the Input file through windows explorer because it is still being used by Matlab which suggests I need to close the stream?

Thank you, Tantalisingly close to getting it to work.

[Guillaume]

This new problem has nothing to do with the .Net code. StandardInput is not a file, and your fopen, fprintf, etc. don't write to it anyway.

Most likely the problem is that you're missing

fclose(fileID);

at the end of your code. If your code is a function, the best way to ensure that the file is closed regardless of what happens (terminates successfully or errors) is to use

fileID =fopen(...  %whatever the fopen code is
cleanupobj = onCleanup(@() fclose(fileID));
%when cleanupobj gets destroyed, either because the function exits normally
%or the function errors, fclose will be called
%... rest of code

[Muhammad Munib]

I've got it to work, I hadn't closed the stream reader so the fopen could not actually write anything to the file. Thank you for your help, much appreciated.

streamreader.close()

Answer 2

[Fangjun Jiang]

Try to run system() manually first or open a command window and then type in line by line

cfd.exe <exp.in
exit

[Muhammad Munib]

Sorry don't quite understand the steps.

Can I write something to exit the exe command window once it finishes its operations.

Thanks.