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Re: find question

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On 30/12/23 01:27, Greg Wooledge wrote:
> On Fri, Dec 29, 2023 at 10:56:52PM +1300, Richard Hector wrote:
>> find $dir -mtime +7 -delete
> 
> "$dir" should be quoted.

Got it, thanks.

>> Will that fail to delete higher directories, because the deletion of files
>> updated the mtime?
>> 
>> Or does it get all the mtimes first, and use those?
> 
> It doesn't delete directories recursively.
> 
> unicorn:~$ mkdir -p /tmp/foo/bar
> unicorn:~$ touch /tmp/foo/bar/file
> unicorn:~$ find /tmp/foo -name bar -delete
> find: cannot delete ‘/tmp/foo/bar’: Directory not empty

Understood.

> But I suppose you're asking "What if it deletes both the file and the
> directory, because they both qualify?"
> 
> In that case, you should use the -depth option, so that it deletes
> the deepest items first.
> 
> unicorn:~$ find /tmp/foo -depth -delete
> unicorn:~$ ls /tmp/foo
> ls: cannot access '/tmp/foo': No such file or directory
> 
> Without -depth, it would try to delete the directory first, and that
> would fail because the directory's not empty.
> 
> -depth must appear AFTER the pathnames, but BEFORE any other arguments
> such as -mtime or -name.

Except that from the man page, -delete implies -depth. Maybe that's a 
GNUism; I don't know.

>> And how precise are those times? If I'm running a cron job that deletes
>> 7-day-old directories then creates a new one less than a second later, will
>> that reliably get the stuff that's just turned 7 days old?
> 
> The POSIX documentation describes it pretty well:
> 
>         -mtime n  The primary shall evaluate as true if the  file  modification
>                   time  subtracted  from  the  initialization  time, divided by
>                   86400 (with any remainder discarded), is n.
> 
> To qualify for -mtime +7, a file's age as calculated above must be at
> least 8 days.  (+7 means more than 7.  It does not mean 7 or more.)

So 7 days and one second doesn't count as "more than 7 days"? It 
truncates the value to integer days before comparing?

Ah, yes, I see that now under -atime. Confusing. Thanks for pushing me 
to investigate :-)

> It's not uncommon for the POSIX documentation of a command to be superior
> to the GNU documentation of that same command, especially a GNU man page.
> GNU info pages are often better, but GNU man pages tend to be lacking.

Understood, thanks. Though it might be less correct where GNUisms exist.

That leaves the question: When using -delete (and -depth), does the 
deletion of files within a directory update the mtime of that directory, 
thereby rendering the directory inelegible for deletion when it would 
have been before? Or is the mtime of that directory recorded before the 
contents are processed?

I just did a quick test (using -mmin -1 instead), and it did delete the 
whole lot.

So I'm still unclear why sometimes the top-level directory (or a 
directory within it) gets left behind. I've just noticed that one of the 
directories (not the one in $dir) contains a '@' symbol; I don't know if 
that affects it?

I'm tempted to avoid the problem by only using find for the top-level 
directory, and exec'ing "rm -r(f)" on it. I'm sure you'll tell me there 
are problems with that, too :-)

Apologies for the slow response - sometimes the depression kicks in and 
I don't get back to a problem for a while :-(

Cheers,
Richard

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find question Richard Hector <richard@walnut.gen.nz> - 2023-12-29 11:00 +0100
  Re: find question Greg Wooledge <greg@wooledge.org> - 2023-12-29 13:30 +0100
    Re: find question Richard Hector <richard@walnut.gen.nz> - 2024-01-13 12:30 +0100
      Re: find question Greg Wooledge <greg@wooledge.org> - 2024-01-13 16:20 +0100

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