Changing environment variables in vimrc
Refer to Vim Wiki’s page on environment variables. The tips uses paths in *nix in the examples. However, for Win*, some inexperienced users don’t know whether slashes or backslashes should be used. In fact, backslashes should be used, and the string should be enclosed by a pair of single quote (I don’t know if double quotes work.) Then things should run. If you’re unlucky and receive a runtime error in the next time you start Vim, then it may be due to the missing space characters around the equal sign.
Writing external commands to files
It’s easy! (:r ![command] will do.)
Writing variables to files
Use the = register. First get into normal mode, then type the
following command.
"=sin(1)p
The p have to be typed before any further changes of contents.
Otherwise, it may not work. For details, see
Unix & Linux Stack Exchange question 8101.
Writing internal commands to files
A forum post has answered my doubt. I redirect interested readers to Object Mix.
(Added on APR 09, 2016)
Fearing that this post will be deleted, I added tianlan’s code below.
:redi @+
:version
:redi END
"+p