fill textbox with current sharepoint user name

[Amit Jain]

i m using infopath and have published forms to sharepoint library. I would
like to populate a text field in form with username of the person opening
the form. we are not using active directory. is there any way where by i
could pull the userid or username the loginname user specifies to log on to
sharepoint site and use it in my infopath form.