File::Find
Sometimes you need to do something to many/all files within certain directory.
use File::Find;
## use a subroutine reference (coderef)
sub process_file {
# do something to each file found
}
find(\&process_file, @DIRLIST);
## or use anonymous subroutine
find(
sub {
# do something to each file found
},
@DIRLIST
}
.. find function from File::Find scans directories in @DIRLIST recursively and for each file or directory calls the referenced function process_file
.. before calling your function find by default changes to the directory being scanned and sets the following (global) variables:
$File::Find::dir– visited directory path relative to the program’s starting directory$File::Find::name– full path of the file being visited relative to the program’s starting directory$_– basename of the file being visited
We are passing both data (the list of directories to search) and behaviour as parameters to the find routine.
We are using the subroutine reference as a callback.
Find the largest file
NOTE: when dereferenced, a subroutine can see all visible lexical variables when reference to the subroutine is taken.
#!/usr/bin/perl
use strict;
use warnings;
use File::Find;
@ARGV = qw(.) unless @ARGV;
my ($biggest_size, $biggest_name) = (-1, "");
sub biggest {
return unless -f && -s _ > $biggest_size;
$biggest_size = -s _;
$biggest_name = $File::Find::name;
}
find(\&biggest, @ARGV);
print "Biggest file $biggest_name in @ARGV is $biggest_size bytes long.\n";
.. _ – virtual filehandle that uses info from the last file lookup (stat - an expensive operation) that a file test operator (-f) performed
Find the most recently changed file
my ($age, $name);
sub youngest {
return if defined $age && $age > (stat($_))[9];
$age = (stat($_))[9];
$name = $File::Find::name;
}
File::Find::Rule
File::Find::Rule CPAN module is an alternative to File::Find:
use File::Find::Rule;
my @txt_files = File::Find::Rule
->file
->name('*.txt')
->in('./');
foreach (@txt_files) {
print "$_\n";
}
More
- Intermediate Perl, Ch. 7
- Perl Cookbook, Recipe 9.7
- Beginners guide to File::Find
- File::Find and permission error handling – using
preprocess