Well I’m used to an application-level view of the file system. A document editor or text editor opens files and saves files, but these are whole-document opera

Well I’m used to an application-level view of the file system. A document editor or text editor opens files and saves files, but these are whole-document operations. I can’t open a document in Sublime Text without reading it, and I can’t save part of a file without saving all of it. So it’s not obvious that these would be different at an OS level. As the post points out, there are uses for Unix’s sub-file-level read-and-write commands, but I’ve never needed them.