# perl - recursive dirctory tasks
# 1. recursively display all file names
print "Listing all files recursively...\n";
recurse(sub {
    my $file = shift;
    print "$file\n";
}, ".");

# 2. find all Java files
print "\nListing all Java files recursively...\n";
recurse(sub {
    my ($file, $pattern) = @_;
    if ($file =~ /$pattern/) {
       print "$file\n";
    }
}, ".", '\.java$');

# 3. find a Java class from a directory
print "\nFinding Java class...\n";
recurse(sub {
    my ($file, $lookfor) = @_;
    if ($file =~ /\.jar$/) {
        my @list = grep {/$lookfor/} `jar -tf $file`;
        if (@list) {
            print "$file:\n";
            print join('', @list), "\n";
        }
    }
    elsif ($file =~ /$lookfor/) {
        print "$file\n";
    }
}, ".", "ClassToFind");

sub recurse {
    my $func = shift;
    my $dir = shift;
    opendir(DIR, $dir) or die "Can't opendir $dir: $!";
    my @files = map "$dir/$_", grep { !/^\.\.?$/ } readdir(DIR);
    closedir DIR;

    foreach $file (@files) {
        if (!-l $file && -d $file) {
            recurse($func, $file, @_);
        }
        else {
            &$func($file, @_);
        }
    }
}