write buffer to a file
[line_range]w [filename] [line_range]wa [filename]
This command writes out the specified lines to a file. If a filename is not given the current file is used. If the line_range is omitted then all lines are written.
If the wa form is used, the editor will append the specified lines to the end of the file.
If a filename is specified and the current filename is not defined, then the specified filename will become the current filename. Note that filename can of course be a device like /dev/par.
Set to the address of the first line written.
Not affected.