DragonFly kernel List (threaded) for 2008-02
Globbing (was Re: HAMMER update 10-Feb-2008)
Bill Hacker wrote:
> But the larger issue is indeed expanded globbing support *somewhere*.
> And not just for new file systems, but old ones that have long-since
> outgrown the currently available resources.
> Massive drive and name space isn't a lot of use if we are short matching
> utils to manage it well.
Filename expansion ("globbing") has nothing to do with
file systems. It is purely a shell feature (and every
shell implements its own). Putting it into the kernel
makes no sense. Note that there are globbing support
functions in libc (POSIX/SUS wants them, and some apps
use them), but no shell uses them, even the base /bin/sh
implements its own filename expansion.
The limit you're talking about ("too many arguments")
is the execve() argument limit. Historically all the
arguments plus environment could not exceed 64 KB.
A few years ago FreeBSD increased the limit to 256 KB.
I don't know if DragonFly did the same, but it doesn't
matter much -- The point is that things like "rm *"
are unsafe if you don't know to what amount the glob
expression will expand. No matter whether the limit
is 64 KB or 256 KB, there _is_ a limit.
That's why xargs(1) exists: "echo * | xargs rm" is
safe (echo is a shell-builtin, so it is not subject to
the execve argument limit).
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