Member Avatar for briskal

Hello everybody,

I have a situation in which I want to execute a command line from a Delphi application, and I want to capture the output from that command and then display it back to the user.

Using CreateProcess I can successfully execute the command - and I am able to accurately determine when the command has finished. The problem comes in trying to capture the output from the command.

First I tried the simplest thing, which was to append > MyOutput.Txt to the lpCommandLine string to redirect the output to a text file. This worked well when I typed the command line directly at a command prompt, but when the command was initiated through CreateProcess the > and MyOutput.Txt were treated as additional parameters for the command, and the output was not redirected.

So then I tried to play with the STARTINFO area and set up a "handle" to which the output should be redirected. Here are excerpts from my code:

{code}
GetStartUpInfo(StartInfo);
StartInfo.dwFlags := StartInfo.dwFlags + STARTF_UseSTDHandles;
StartInfo.wShowWindow := sw_ShowNormal; // so I can see whether or not output is redirected
StartInfo.hStdInput := 0;
StartInfo.hStdOutput := TTextRec(MsgFile).Handle; // Text file handle
StartInfo.hStdError := 0;
FillChar(ProcsInfo, SizeOf(ProcsInfo), #0);

CreateProcess(nil, @RunProgName[1], nil, nil,
True, // bInheritHandles
0, // dwCreationFlags - use defaults
nil, // lpEnvironment
@StartingDirectory[1],
StartInfo,
ProcsInfo);

{/code}

The result with the above code is that the output is redirected (it is not displayed in the "DOS" window), but it is not redirected into the MsgFile. In fact, I do not know where it went! Whether or not MsgFile is open within the Delphi application when CreateProcess is executed, the results are the same - output is redirected ... to nowhere? I do not see any error messages (compiler or run-time).

Can anybody help me here? How should I set up hStdOutput so that I can access the output text when the command has finished?

Thank you!

briskal

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Member Avatar for briskal

Further to the above - more trial and error led me to a workable solution to my own problem:

I included the text CMD /C at the beginning of the lpCommandLine string which also had > MyOutput.Txt at the end. The command interpreter then parsed the command string correctly and the standard outpur was redirected to MyOutput.Txt.

I was not able to get anything working properly using the hStdOuput handle withing the STARTINFO block, but, for my application, now I don't need to!

briskal

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