James B. Byrne wrote:
> On Sat, January 23, 2010 20:21, Robert Nichols wrote:
>> Robert Heller wrote:
>
>> Gosh, then I guess the manpage for 'find' must be totally wrong
>> where it
>> says:
>>
>> -exec command ;
>> ...
>> The specified command is run once for each matched
>> file.
>>
>
> Not wrong. The man page on find simply does not speak to the limits
> of the kernal configuration (MAX_ARG_PAGES) implicitly used by cp,
> find, ls, etc. It just lives within its means and fails when these
> do not suffice.
>
> The problem you have is that the selection of all qualified files is
> completed before any are acted on by find. So, in the case of
> overlarge collections, the page limit is exceeded before any are
> deleted. Taking each file as it is found and piping it to an
> external rm command avoids hitting the page limit.
When using the -exec action with the ";" terminator, the constructed
command line always contains the path for exactly one matched file.
Try it. Run "find /usr -exec echo {} ;" and see that you get one
path per line and output begins almost instantly. Do you really
believe that 'find' searched the entire /usr tree in that time?
Now if the "{}" string appears more than once then the command line
contains that path more than once, but it is essentially impossible
to exceed the kernel's MAX_ARG_PAGES this way.
The only issue with using "-exec command {} ;" for a huge number of
files is one of performance. If there are 100,000 matched files,
the command will be invoked 100,000 times.
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.
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