programmatically press an enter key after starting .exe file in Matlab

Question

In Matlab I can start external .exe files that sometime have a pop up that requires an enter key pressed. For example:

system('C:\Program Files (x86)\WinZip\WINZIP32.EXE')

will start Winzip, and then in order to use it you need to pass the "buy now" pop up window by pressing enter. Now my problem is not with winzip, I only gave it as an example (i use winrar anyway :).

How can I programmatically press an enter key in Matlab in such cases ? (I use win 7)

Can an event listener be used to solve that?

EDIT: The java.awt.Robot class indeed works on explorer, but not on any software that has a pop up window with an OK button that needs to be pressed. I don't know why it doesn't work for that. I gave the winzip example because I assume everybody has winzip/winrar installed in their machine. The actual software I have is different and irrelevant for the question.

Answer 1

There is a way using Java from Matlab, specifically the java.awt.Robot class. See here.

Apparently there are two types of programs, regarding the way they work when called from Matlab with system('...'):

1. For some programs, Matlab waits until the program has finished before running the next statement. This happens for example with WinRAR (at least in my Windows 7 machine).

2. For other programs this doesn't happen, and Matlab proceeds with the next statement right after the external program has been started. An example of this type is explorer (the standard Windows file explorer).

Now, it is possible to return execution to Matlab immediately even for type 1 programs: just add & at the end of the string passed to system. This is standard in Linux Bash shell, and it also works in Windows, as discussed here.

So, you would proceed as follows:

robot = java.awt.Robot;
command = '"C:\Program Files (x86)\WinRAR\WinRAR"'; %// external program; full path
system([command ' &']); %// note: ' &' at the end
pause(5) %// allow some time for the external program to start
robot.keyPress (java.awt.event.KeyEvent.VK_ENTER); %// press "enter" key
robot.keyRelease (java.awt.event.KeyEvent.VK_ENTER); %// release "enter" key

Answer 2

If your applications are only on Windows platform, you can try using .net objects.

The SendWait method of the SendKeys objects allows to send virtually any key, or key combination, to the application which has the focus, including the "modifier" keys like Alt, Shift, Ctrl etc ...

The first thing to do is to import the .net library, then the full syntax to send the ENTER key would be:

NET.addAssembly('System.Windows.Forms');
System.Windows.Forms.SendKeys.SendWait('{ENTER}'); %// send the key "ENTER"

If you only do it once the full syntax is OK. If you plan to make extensive use of the command, you can help yourself with an anonymous helper function.

A little example with notepad

%% // import the .NET assembly and define helper function
NET.addAssembly('System.Windows.Forms');
sendkey = @(strkey) System.Windows.Forms.SendKeys.SendWait(strkey) ;

%% // prepare a few things to send to the notepad
str1 = 'Hello World' ;
str2 = 'OMG ... my notepad is alive' ;
file2save = [pwd '\SelfSaveTest.txt'] ;
if exist(file2save,'file')==2 ; delete(file2save) ; end %// this is just in case you run the test multiple times.

%% // go for it
%// write a few things, save the file then close it.
system('notepad &') ;   %// Start notepad, without matlab waiting for the return value
sendkey(str1)           %// send a full string to the notepad
sendkey('{ENTER}');     %// send the {ENTER} key
sendkey(str2)           %// send another full string to the notepad
sendkey('{! 3}');       %// note how you can REPEAT a key send instruction
sendkey('%(FA)');       %// Send key combination to open the "save as..." dialog
pause(1)                %// little pause to make sure your hard drive is ready before continuing
sendkey(file2save);     %// Send the name (full path) of the file to save to the dialog
sendkey('{ENTER}');     %// validate
pause(3)                %// just wait a bit so you can see you file is now saved (check the titlebar of the notepad)
sendkey('%(FX)');       %// Bye bye ... close the Notepad

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As explained in the Microsoft documentation the SendKeys class may have some timing issues sometimes so if you want to do complex manipulations (like Tab multiple times to change the button you actually want to press), you may have to introduce a pause in your Matlab calls to SendKeys.

Try without first, but don't forget you are managing a process from another without any synchronization between them, so timing all that can require a bit of trial and error before you get it right, at least for complex sequences (simple one should be straightforward).

In my case above for example I am running all my data from an external hard drive with an ECO function which puts it into standby, so when I called the "save as..." dialog, it takes time for it to display because the HDD has to wake up. If I didn't introduce the pause(1), sometimes the file path would be imcomplete (the first part of the path was send before the dialog had the focus).

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Also, do not forget the & character when you execute the external program. All credit to Luis Mendo for highlighting it. (I tend to forget how important it is because I use it by default. I only omit it if I have to specifically wait for a return value from the program, otherwise I let it run on its own)

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The special characters have a special code. Here are a few:

Shift          +
Control (Ctrl)  ^
Alt            %

Tab            {TAB}
Backspace      {BACKSPACE}, {BS}, or {BKSP}
Validation     {ENTER} or ~ (a tilde)
Ins Or Insert  {INSERT} or {INS}
Delete         {DELETE} or {DEL}

Text Navigation {HOME} {END} {PGDN} {PGUP}
Arrow Keys      {UP} {RIGHT} {DOWN} {LEFT}

Escape          {ESC}
Function Keys   {F1} ... {F16}
Print Screen    {PRTSC}
Break           {BREAK}

The full list from Microsoft can be found here

Answer 3

There is a small javascript utility that simulates keystrokes like this on the Windows javascript interpreter.

Just create a js file with following code:

var WshShell = WScript.CreateObject("WScript.Shell");
WshShell.SendKeys(WScript.Arguments(0));

then call it from Matlab after the necessary timeout like this:

system('c:\my\js\file\script.js {Enter}');

Can't test here now, but I think this should work...