saves the current document using the specified string as the file name.
If the optional filename argument is not specified, the
file requester will open and you will be prompted to select a file. (You
can inhibit the file requester opening by using the
command; see NoFileReq.)
If you escape from the file requester, you can enter the file name on the input line, the default being the current document name, if available.
If the file has been modified since the current document was loaded or last
saved (perhaps by another user),
ne will warn you before overwriting
the updated file.