On 07/16/11 16:37, Hans-Peter Diettrich wrote:
> There seems to exist an issue with (output) redirection, when I try to
> run an external program from code. What I want to achieve is this:
>
> In a Win32 console I can run
>>diff -r dir1 dir2 > diff.txt
>
> When I use e.g. Exec('diff', args), diff complains about an excess
> argument, it works when "> diff.txt" is removed. With other functions I
> had less luck (ExecuteProcess, CreateProcess...), no output at all.
>
> Now I assume that output redirection is a shell feature, not available
> in direct invocation of an external program. Right?
>
> Does there exist a simple way to run "diff", and to redirect its output
> into an file? A batch file? Platform independence would be nice, of course.
>
> DoDi
>
> _____
The best way I know is described here:
http://wiki.lazarus.freepascal.org/Executing_External_Programs#How_to_redirect_output_with_TProcess
something like the following (not tested)
function RunCommandAndDirectOutput(ACommand, AArgs, AOutName: String):
Integer;
var
proc: TProcess;
data: TFileStream;
buffer: array [0..511] of byte;
count: Integer;
begin
proc := TProcess.Create(nil);
proc.commandline := ACommand + ' ' + AArgs;
proc.options := [pousepipes];
data := TFileStream.Create(AOutName, fmcreate or fmwrite);
proc.Execute;
while proc.running or proc.output.numbytesavailable > 0 do
begin
count := proc.output.numbytesavailable;
if count > 512 then
count := 512;
count := proc.output.read(buffer, count);
data.write(buffer, count);
end;
Result := Proc.ExitStatus;
proc.free;
data.free;
end;
usage:
RunCommandAndDirectOutput('diff', '-r dir1 dir2', 'diff.txt');
Regards,
Andrew Haines
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