Re^3: Apache/CGI fcould not use Spreadsheet::ParseExcel

[LanX]

So is Perl accessing modules without checking the surrounding directory?

Probably...

At least in the case of perldoc - which is not relevant here - r would be needed on directories.

[afoken]

So is Perl accessing modules without checking the surrounding directory?

Probably...

Yes. Why should it be done in any other way? Perl needs to read some files with known names. So for each file, it calls open(), perhaps through several layers of libraries. That may succeed or fail. Why should perl (or any other application) check directories for that? Even stat() and lstat() only need execute permission on all of the directories leading to the file passed to stat()/lstat(), no read permissions.

The operating system does check the directories, like the desired file, for sufficient permissions and other things. See "ERRORS" in open() and path_resolution.

The only reason for needing read permissions on a directory is when you need a list of file names, e.g. for an (insecure) plugin system that loads all files as plugins that match some criteria on file names.

Nevertheless, directories commonly have either both r and x bits sets, or none of them. Having only the r bit set does not make much sense, having only the x bit set may be useful in some security-related scenarios.

Alexander

[LanX]

> > So is Perl accessing modules without checking the surrounding directory?

> Why should it be done in any other way?

because Perl may choose between different extensions.

.plc , .pmc and .pod come to mind.

Of course this can be done without r-flag, but I wouldn't recommend o-r on directories unless for special reasons.

[afoken]

because Perl may choose between different extensions.

.plc , .pmc and .pod come to mind.

I doubt that perl would create a list of directories and grep for those files that have matching extensions. Simply because it is too much work. It is much easier to concat the base filename and the extensions one after the other, until one can be opened. Roughly like this:

# perlish pseudo-code, too lazy for C today
sub tryLoadMod
{
    my $basename=shift;
    for my $ext (qw(pm pmc plc pod aua wtf)) {
        if (open my $handle,'<',"$basename.$ext") {
            compileAndRun($handle);
            last;
        }
    }
}

Alexander

[bliako]

So is Perl accessing modules without checking the surrounding directory?

Perl is asking the operating system for the files. If the OS thinks it's OK it returns the contents of the files, otherwise it doesn't and one gets permission denied. In my linux, reading a file is permitted when the surrounding directory has "x" set (executable bit) for the reader user.