const
  libc = '/usr/lib/libc.dylib';

type
  PIOFile = Pointer;

//Create a new stream connected to a pipe running the given command.
function popen(const Command: PAnsiChar; Modes: PAnsiChar): PIOFile; cdecl;
  external libc name '_popen';

//Close a stream opened by popen and return the status of its child.
function pclose(Stream: PIOFile): Integer; cdecl; external libc name '_pclose';

//Return the EOF indicator for STREAM.
function feof(Stream: PIOFile): Integer; cdecl; external libc name '_feof';

//Read chunks of generic data from STREAM.
function fread(Ptr: Pointer; Size: LongWord; N: LongWord;
  Stream: PIOFile): LongWord; cdecl; external libc name '_fread';

//Wait for a child to die.  When one does, put its status in *STAT_LOC
//and return its process ID.  For errors, return (pid_t) -1.
function wait(__stat_loc: PInteger): Integer; cdecl;
  external libc name '_wait';

procedure ExecCmdine(const CmdLine: string; CmdResult: TStrings);
var
  Output: PIOFile;
  Buffer: PAnsiChar;
  TempString: Ansistring;
  Line: AnsiString;
  BytesRead: Integer;
const
  BufferSize: Integer = 1000;
begin
  TempString := '';
  Output := popen(PAnsiChar(Ansistring(CmdLine)), 'r');
  GetMem(Buffer, BufferSize);
  if Assigned(Output) then
  try
    while feof(Output) = 0 do
    begin
      BytesRead := fread(Buffer, 1, BufferSize, Output);
      SetLength(TempString, Length(TempString) + BytesRead);
      Move(Buffer^, TempString[Length(TempString) - (BytesRead - 1)], BytesRead);

      while Pos(#10, TempString) > 0 do
      begin
        Line := Copy(TempString, 1, Pos(#10, TempString) - 1);
        if CmdResult <> nil then
          CmdResult.Add(UTF8ToString(Line));

        TempString := Copy(TempString, Pos(#10, TempString) + 1, Length(TempString));
      end;
    end;
  finally
    pclose(output);
    wait(nil);
    FreeMem(Buffer, BufferSize);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Strings: TStrings;
begin
   Strings := TStringList.Create;
   ExecCmdine('ifconfig', Strings);
   Memo1.Lines := Strings;
end;