File Output Issues.

I used to be able to use the output setting to send an image render to a file name
and format of my choice, when doing an image render. Now, I have to save
my image secondarily after render in the internal image editor.

-What went wrong? How may I have blender write my image file via the output setting again?

-It is possible to run blender from the command line. How may I get blender to
background render a file which is only a single image, when in this command line
background mode?

If you mean the output options in the render settings this is for and has always been just for animations.

If you want to render an image directly to a file then use the compositor and use the file output node