I'm working with TProcess, which for the most part I love, but I'm scratching my head right now because of a problem I'm experiencing.
Suppose I have the following command:
ifconfig | grep -E -e "inet6? addr:" | grep -v -E -e "(127.0.0.1|::1|Scope:Link)" | sed -e
"s/^.*addr:\s*\(\S*\)\(\/\d+\)*.*$/\1/g"
I can run that as-is from the command-line, since my shell hooks up all of the pipes and whatnot for me. Also, I can execute it like this:
bash -c "ifconfig | grep -E -e \"inet6? addr:\" | grep -v -E -e \"(127.0.0.1|::1|Scope:Link)\" | sed -e
\"s/^.*addr:\s*\(\S*\)\(\/\d+\)*.*$/\1/g\""
By escaping the double-quotes and then passing the whole thing to bash as the argument for the -c, it works.
However, if I pass the above command (the one using bash -c with the double-quotes of the original command escaped), as the CommandLine of a TProcess, it doesn't work. TProcess execs bash, but the argument doesn't seem to make it there correctly. Bash spits out:
$ ./tprocquotes
addr:\" | grep -v -E -e \"(127.0.0.1|::1|Scope:Link)\" | sed -e \"s/^.*addr:\s*\(\S*\)\(\/\d+\)*.*$/\1/g\"": -c: line 0: unexpected EOF while looking for matching `"'
addr:\" | grep -v -E -e \"(127.0.0.1|::1|Scope:Link)\" | sed -e \"s/^.*addr:\s*\(\S*\)\(\/\d+\)*.*$/\1/g\"": -c: line 1: syntax error: unexpected end of file
Yes, I know I could use single quotes instead of double quotes to the -c argument, and then I wouldn't have to escape the double-quotes. And, yes, I know there are other ways to accomplish what that command does by parsing the output of ifconfig. I've got workarounds for this particular example, but I still don't know why it shouldn't work with TProcess with me escaping the double-quotes with a backslash and then passing the whole thing double-quote enclosed to bash -c as the TProcess CommandLine.
What am I doing wrong?
I've got an example program illustrating what I'm doing on PasteBin at http://pastebin.com/f336d384b, and I'll also include the contents of the program in this email in case anyone in the future's ever searching the archives and the pastebin link doesn't exist any more.
-SG
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program tprocquotes;
{$mode objfpc}{$H+}uses
{$IFDEF UNIX}
cthreads,
{$ENDIF}
Classes,
SysUtils,
dateutils,
process,
pipes; function ExecuteProcess(const command : string;
out commandExitCode : integer;
const timeoutSec : integer;
const stdout_stream : TStream;
const stderr_stream : TStream;
const redirectErr : boolean) : boolean;
const
READ_BYTES = 2048;
var
P : TProcess;
buffer : array of byte;
tmpStdOutput : TMemoryStream;
tmpStdError : TMemoryStream;
stdOutToUse : TStream;
stdErrToUse : TStream;
startTime : TDateTime;
stdOutBytesRead : longword;
function ReadAvailableBytes(const source_stream : TInputPipeStream;
const dest_stream : TStream) : longword;
var
bytes_available : longword;
bytes_read : longint;
bytes_to_read : longint;
begin
result := 0;
if Assigned(source_stream) and Assigned(dest_stream) then begin
bytes_available := source_stream.NumBytesAvailable;
while (bytes_available > 0) do begin
if (bytes_available >= READ_BYTES) then begin
bytes_to_read := READ_BYTES;
end else begin
bytes_to_read := bytes_available;
end;
bytes_read := source_stream.Read(buffer[0], bytes_to_read);
if (bytes_read > 0) then begin
dest_stream.Write(buffer[0], bytes_read);
result := result + longword(bytes_read);
end;
bytes_available := source_stream.NumBytesAvailable;
end;
end;
end;
begin
result := true;
commandExitCode := 1;
if Assigned(stdout_stream) then begin
tmpStdOutput := nil;
stdOutToUse := stdout_stream;
end else begin
tmpStdOutput := TMemoryStream.Create;
stdOutToUse := tmpStdOutput;
end;
stdOutToUse.Size := 0;
stdOutToUse.Seek(0, soFromBeginning);
if Assigned(stderr_stream) then begin
tmpStdError := nil;
stdErrToUse := stderr_stream;
end else begin
tmpStdError := TMemoryStream.Create;
stdErrToUse := tmpStdError;
end;
stdErrToUse.Size := 0;
stdErrToUse.Seek(0, soFromBeginning);
SetLength(buffer, READ_BYTES);
P := TProcess.Create(nil);
try
P.CommandLine := command;
P.Options := [poUsePipes];
if redirectErr then P.Options := P.Options + [poStderrToOutPut];
P.InheritHandles := false;
startTime := now;
P.Execute;
{ read stdout while the process runs }
while P.Running do begin
stdOutBytesRead := ReadAvailableBytes(P.Output, stdOutToUse);
if (stdOutBytesRead = 0) and
(ReadAvailableBytes(P.Stderr, stdErrToUse) = 0) then begin
sleep(100);
end;
{ check timeout }
if (timeoutSec > 0) and (SecondsBetween(now, startTime) >
timeoutSec) then begin
result := false;
P.Terminate(1);
P.WaitOnExit; // avoid a zombie process
break;
end;
end;
commandExitCode := P.ExitStatus;
{ read what's left over in stdout }
ReadAvailableBytes(P.Output, stdOutToUse);
{ read what's left over in stderr }
ReadAvailableBytes(P.Stderr, stdErrToUse);
finally
if Assigned(tmpStdError) then FreeAndNil(tmpStdError);
if Assigned(tmpStdOutput) then FreeAndNil(tmpStdOutput);
FreeAndNil(P);
SetLength(buffer, 0)
end;
end;
const
COMMAND = 'bash -c "ifconfig | grep -E -e \"inet6? addr:\" | grep -v
-E -e \"(127.0.0.1|::1|Scope:Link)\" | sed -e
\"s/^.*addr:\s*\(\S*\)\(\/\d+\)*.*$/\1/g\""';
var
stdOutStream : THandleStream;
stdErrStream : THandleStream;
commandExitCode : integer;
begin
stdOutStream := THandleStream.Create(StdOutputHandle);
stdErrStream := THandleStream.Create(StdErrorHandle);
try
if ExecuteProcess(COMMAND, commandExitCode, 120, stdOutStream,
stdErrStream, false) then begin
ExitCode := commandExitCode;
end else begin
ExitCode := 1;
end;
finally
FreeAndNil(stdOutStream);
FreeAndNil(stdErrStream);
end;
end.
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