In addition to selected answer above,
when using the mouse to select (1),
and the problem of only copying whole lines mentioned by the comment
of @dronus to it, when just wanted to partly copy lines (2):
(1) At my Debian based DietPi (Raspberry PI)system, vim acts a little different like in the preferred solution above when using the mouse to enter and select 'VISUAL MODE' on my Ubuntu 16.04 work station. Then
but if I type ':' for command, it will not show up with the
'<,'>
where I can just simply add my
w new.txt
after it. So I just typed it by myself and it did work:
'<,'>w new.txt
and it copies the whole line(s) yanked content to my file 'new.txt', whereas '<,' seem to mean 'copy selected lines and '>' redirect it to the write command's referenced file.
(2) And to the problem of not pasting part of the line(s), like in @dronus comment mentioned, this solution (the selected one, first alternative) worked for me:
Edit the first file, yanking the text you want. Then open your second file from within vi (:e /path/to/other/file) and paste it (by typing p). Save it (like above ':w new.txt'.
It will then just copy the part of the lines marked up by mouse or 'y' with the cursors.
[EDIT] On my Ubuntu system: Sometimes selecting by mouse does NOT enter 'VISUAL MODE' in vim. Then the normal copy/paste can be selected using the context menu... I have not found the reason why Ubuntu changed it behaviour from a 'client acting behaviour' to a 'host' one (withUbuntu hosting the ssh bash window to my 'Client')...