On 10/28/09 Wed Oct 28, 2009 3:18 PM, "Harry Putnam" <rea...@newsguy.com>
scribbled:
> Jim Gibson <jimsgib...@gmail.com> writes:
>
>> If you want to process files in a certain order, then save the files in an
>> array. When find is finished, sort that array and process the files in any
>> order. For example, if you want to process files in chronological order, in
>> the wanted routine save the file path and age as an array entry (untested):
>>
>> my @files;
>> my $dir = '/some/directory/path';
>>
>> find( sub{
>> my $age = -M $File::Find::name;
>> push( @files, [ $File::Find::name, $age ] );
>> }, $dir);
>>
>> for my $entry ( sort { $a->[1] <=> $b[1] } @files ) {
>> my($file,$age) = @$entry;
>> # process file
>> }
>>
>> (reverse $a and $b if you want the reverse order).
>
> I see the final result but am slightly mystified by some of the
> notation. First off the formulation of the find() function.
>
> I've seen it before but don't really understand it.
>
> Seems like the guts of find() are missing, but I know they are not.
>
> I guess it could be expressed:
>
> find( sub{..results of this sub routine},$dir);
Yes, that is correct. The line
find( sub { ... ], $dir);
that contains the definition of an anonymous subroutine is equivalent to
sub wanted { ... };
find( \&wanted, $dir );
which uses a named subroutine. Surprisingly, the documentation for
File::Find does not mention this use of anonymous subroutine references.
>
> Like you might do with `find($var1,$var2);'
> But there you would expect to see `find()' have some lines of
> processing to the two elems of @_ passed in.
The find() function of File::Find expects two or more arguments. The first
argument must be a subroutine reference. This subroutine is called by find()
for each directory and file found. The second and any subsequent arguments
are directories to search.
>
> What are the brackets ([]) doing here:
> push( @files, [ $File::Find::name, $age ] );
The brackets create a reference to an anonymous array with the specified
context. The references is then pushed onto the @files array.
>
> and what is this creature:
> my($file,$age) = @$entry;
This line dereferences the reference to the anonymous array saved in each
element of @files and assigns the contents of each anonymous array to the
scalar variables $file and $age.
See 'perldoc perllol' for more details on constructing and accessing nested
data structures in Perl.
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