I'm familiarizing myself with TProcess, so I decided to write a simple
routine which executes a command and puts STDOUT/STDERR in a
stringlist:
-------------------------
procedure ExecCommand(const command : string;
const stdout : TStringList;
const stderr : TStringList;
const timeoutSec : integer;
out exitStatus : integer);
const
READ_BYTES = 2048;
var
P: TProcess;
nOut : LongInt;
nErr : LongInt;
StdOutput : TMemoryStream;
StdOutBytesRead: LongInt;
StdError : TMemoryStream;
StdErrBytesRead: LongInt;
startTime : TDateTime;
begin
exitStatus := -1;
StdOutput := TMemoryStream.Create;
StdError := TMemoryStream.Create;
StdOutBytesRead := 0;
StdErrBytesRead := 0;
try
P := TProcess.Create(nil);
try
P.CommandLine := command;
P.Options := [poUsePipes];
startTime := now;
P.Execute;
{ read stderr and stdout while the process runs }
while P.Running do begin
StdOutput.SetSize(StdOutBytesRead + READ_BYTES);
StdError.SetSize(StdErrBytesRead + READ_BYTES);
nOut := P.Output.Read((StdOutput.Memory + StdOutBytesRead)^,
READ_BYTES);
if nOut > 0 then begin
Inc(StdOutBytesRead, nOut);
end;
nErr := P.Stderr.Read((StdError.Memory + StdErrBytesRead)^, READ_BYTES);
if nErr > 0 then begin
Inc(StdErrBytesRead, nErr);
end;
if (nErr = 0) and (nOut = 0) then Sleep(100);
if (timeoutSec > 0) and (SecondsBetween(now, startTime) >
timeoutSec) then begin
P.Terminate(exitStatus);
raise Exception.Create('Execution timed out');
end;
end;
exitStatus := P.ExitStatus;
{ read what's left over in stdout }
repeat
StdOutput.SetSize(StdOutBytesRead + READ_BYTES);
nOut := P.Output.Read((StdOutput.Memory + StdOutBytesRead)^,
READ_BYTES);
if nOut > 0 then begin
Inc(StdOutBytesRead, nOut);
end;
until nOut <= 0;
{ read what's left over in stderr }
repeat
StdError.SetSize(StdErrBytesRead + READ_BYTES);
nErr := P.Stderr.Read((StdError.Memory + StdErrBytesRead)^, READ_BYTES);
if nErr > 0 then begin
Inc(StdErrBytesRead, nErr);
end;
until nErr <= 0;
StdOutput.SetSize(StdOutBytesRead);
if Assigned(stdout) then begin
stdout.LoadFromStream(StdOutput);
end;
StdError.SetSize(StdErrBytesRead);
if Assigned(stderr) then begin
stderr.LoadFromStream(StdError);
end;
finally
FreeAndNil(StdOutput);
FreeAndNil(StdError);
FreeAndNil(P);
end;
except
on E : Exception do begin
exitStatus := -1;
if Assigned(stderr) then begin
stderr.Add(E.Message);
end;
end;
end;
end;
-------------------------
Everything works fine unless the output to STDOUT of the command
exceeds 65K (I'm testing it by running "cat /path/to/some/file" as the
command). When this happens, the P.Stderr.Read inside the while loop
just hangs and never returns.
What am I doing wrong?
-SG
========================
Computer over. Virus = very yes.
Seth Grover
sethdgrover[at]gmail[dot]com
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