Re: ls -l|head seems to look at all files in directory

[Reuben Thomas]

On Mon, 25 May 2009, Jim Meyering wrote:

> Pádraig Brady wrote:
>
> > Reuben Thomas wrote:
> > > On Mon, 25 May 2009, Jim Meyering wrote:
> > >
> > > > To do what he wants you have to know that ls -1U is the only
> > > > way to get one output entry per readdir call.
> > > >
> > > > Reuben, you want to do it like this:
> > > >
> > > >  ls -1U|head|xargs ls -l
> > >
> > > Thanks for the hint about -1, but this doesn't seem to make any
> > > difference: I run "ls -1U|head" in a directory with lots of files (about
> > > 10,000) and it pauses for a minute or so before giving me my ten lines
> > > of output.
> > >
> > > If I run the command again, then of course it runs almost instantly, so
> > > I'm not sure what use the loops are in the tests you give.
> >
> > With the ls on fedora 8 (coreutils 6.9) I see all the
> > redundant getdents64() calls when using strace on Jim's command above.
> > With the latest coreutils I do not.
>
> Right.  The change that made ls -1U more efficient was after 6.12
> [v6.12-113-g8d974b0]:

Ah, I'm using 6.10. Thanks for the clarification.

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