method seekToEnd

This method changes the position of the stream to be at the end of the stream.

var fileStreamObj = shell.serviceManager.basics.fileStream;
var streamWriterObj = shell.serviceManager.basics.rawStreamWriter;

fileStreamObj.openForWrite("c:\\temp\\test.txt", false, false);
streamWriterObj.stream = fileStreamObj;

//to make sure the position will be at the end for next write
//in case of seekRelative or seekToStart been called
fileStreamObj.seekToEnd();

fileStreamObj.close();