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;