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Blocking on WinExec in Delphi 1.0

Posted on 1997-10-29
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Last Modified: 2012-05-04
Is there a way to spawn a process in Delphi 1.0 and wait for it to run to completion?  WinExec() continues without waiting for the process to complete.
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Question by:mozack
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Accepted Solution

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98113772 earned 100 total points
ID: 1349131
Hi,

Try this one:

Function WinExecAndWait(Path : string; Visibility : word) : word;
var
  InstanceID : THandle;
  PathLen : integer;
begin
  { inplace conversion of a String to a PChar }
  PathLen := Length(Path);
  Move(Path[1],Path[0],PathLen);
  Path[PathLen] := #0;
  { Try to run the application }
  InstanceID := WinExec(@Path,Visibility);
  if InstanceID < 32 then { a value less than 32 indicates an Exec error }
     WinExecAndWait := InstanceID
  else
  begin
    Repeat
      Application.ProcessMessages;
    until Application.Terminated or (GetModuleUsage(InstanceID) = 0);
    WinExecAndWait := 32;
  end;
end;


<--- Cut --->

Greatings from Denmark
Claus Ziegler
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Author Comment

by:mozack
ID: 1349132
No. ProcessMessages gives the control back to windows. The code
is fine.
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Expert Comment

by:krisz
ID: 1349133
Hi,

No draining of the CPU is done. My answer is right. the "ProcessMessages" gives control back to windows.

Greatings from Denmark
Claus Ziegler
0
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Expert Comment

by:98113772
ID: 1349134
I'm running this process on Windows NT, I don't know if this has anything to do with performance, but when I run:

Repeat
   Application.ProcessMessages;
Until Application.Terminated;

Some 97% of the CPU gets used.  When I start up other processes, the other processes have to fight for CPU usage with this process.
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Author Comment

by:mozack
ID: 1349135
Yes, but it only uses the 97% when noone else needs it. As you can see, it will get lower and lower when you starts more processes up.

Greatings from Denmark
Claus Ziegler
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Expert Comment

by:98113772
ID: 1349136
Exactly, whereas a real Sleep() would not use any CPU at all.
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