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How do I run a command-line program in Delphi?

Answer 1

+5 A:

An example using ShellExecute():

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShellExecute(0, nil, 'cmd.exe', '/C find "320" in.txt > out.txt', nil, SW_HIDE);
  Sleep(1000);
  Memo1.Lines.LoadFromFile('out.txt');
end;

Note that using CreateProcess() instead of ShellExecute() allows for much better control of the process.

Ideally you would also call this in a secondary thread, and call WaitForSingleObject() on the process handle to wait for the process to complete. The Sleep() in the example is just a hack to wait some time for the program started by ShellExecute() to finish - ShellExecute() will not do that. If it did you couldn't for example simply open a notepad instance for editing a file, ShellExecute() would block your parent app until the editor was closed.

mghie 2009-09-21 13:34:32

Shouldn't that be Memo1.Lines.LoadFromFile('out.txt');

IanH 2009-09-21 13:38:27

Indeed, thanks for spotting it.

mghie 2009-09-21 13:40:14

Er, if the windows is hidden (SW_HIDE), why should we put a Sleep(1000) after the ShellExecute ?

gramm 2009-09-21 13:58:35

I'm working with 100MB text files so I'm going for the WaitForSingleObject option. thanks ! :)

gramm 2009-09-21 14:28:54

`ShellExecute()` will start the application but not wait for it to finish - otherwise you couldn't really use it to open a standard GUI program. It may not matter with running `find` on a small text file, but for longer executing tasks you have to make sure they are finished before you process the results in `out.txt`. That's why using `CreateProcess()` and waiting on the process handle is a much better way to do it.

mghie 2009-09-21 14:32:22

Alternatively use ShellExecuteEx, which can be used with wait functions

Gerry 2009-09-22 00:39:35

Answer 2

+3 A:

If you want to catch the output, you're looking for CreateProcess, with the handles in place to catch standard-input:

http://www.delphi3000.com/articles/article%5F3361.asp (and many others if you Google around)

Stijn Sanders 2009-09-21 13:35:20

Not necessary if the executed application accepts input from a file whose name is given as a parameter.

mghie 2009-09-21 13:39:21

This IS the way to go. Redirect the output to your application and you circumvent problems with missing IO permissions and file deletion after processing the output.

Scoregraphic 2009-09-21 14:38:08

@Scoregraphic: I agree that `CreateProcess()` is the way to go. Input redirection however isn't always necessary. Output redirection may be necessary, but that's for the OP to decide. There is value in developing only as much as strictly necessary.

mghie 2009-09-21 15:19:31

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