Otherwise it still might be useful, but in general it's kind of unnecessary. It adds logic to your application that it doesn't need, which violates "do one thing, and one thing very well" (albeit only a very small violation).
Sure. However, for example, GNU sort doesn't work that way. Most utilities don't work that way. Most utilities accept a file as an source of input, and most of those don't act on the inode. That's the status quo.
sort < bigfile > bigfile
$ sort "$name" | sponge "$name"
$ sort -o "$name" "$name"
I'm wondering if there's any practical use for the behaviour, or if it's worth hacking a shell such that it produces a warning/interactive confirm prompt for it (or transparently buffers to DWIM maybe?)
Picking one input to still be consumed from stdin can make sense, though. A special case of this is config files, which are almost never read from stdin (they usually have a default location or several).
There are few usage scenarios where such behavior isn't enough, like for example fsck, but even there this paradigm is flexible enough to work - for such applications could be split into an analyzer and a repair program. There is nothing stopping one from outputting a binary data stream on stdout; Lots of applications do exactly that on UNIX, compressors come to mind.
What use case have you where stdout/stdin/stderr isn't enough on an operating system family where the core paradigm of usage is that everything is a binary stream of data?
Please note that we already agree here.
> What use case have you where stdout/stdin/stderr isn't enough on an operating system family where the core paradigm of usage is that everything is a binary stream of data?
My argument isn't that I have a use case where it 'isn't enough.' My argument is that many people come to a cli utility expecting that <foo /path/to/myfile> simply works.
So are for or against that? If you're for the < /path/to/my/file argument, then we are in complete agreement. A command line application should read from stdin where that applies.
I think `foo /path/to/myfile` is what the parent was trying to say.