Try this:
file=WriteFile(file_req$)
tl=TextAreaLen(textarea1,2)
For i=0 To tl
tx$=TextAreaText$(textarea1,i,1,2)
tnl=Len(tx$)
For ii=0 To tnl
If Mid$(tx$,ii,1)=Chr$(10) ;Strip line break
tx$=Mid$(tx$,1,ii-1) ;Write result
EndIf
Next
WriteLine file,tx$
Next
CloseFile file
Bye.