Background:

I am a developer working on a wxPerl application distributed to end users on multiple platforms. Part of the app includes a file transfer manager that allows the user to choose a download directory for file transfers from the server.

The Issue:

We've had issues with users not having write permissions to the download directory they choose.

The Intended Solution:

When the user sets their download directory, or adds a new download, confirm they have write access to the download directory with a '-w $path' check. If they do not have write access prompt for a different download directory.

The Problem:

'-w $path' is not fully cross platform compatible. It works great on Linux but has issues on Mac and Windows. Consider the following script:

use strict;
use warnings;

my $path = $ARGV[0];

exit unless $path;

if ( -w $path ) {
   print "'$path' is writeable\n";
   eval {
      open my $fh, '>', "$path/foo.txt" or die $!;
      print $fh "foo\n";
      close $fh;
   };
   if ( $@ ) {
      print "\twrite failed: '$@'\n";
   }
   else {
      print "\twrite succeeded\n";
      unlink "$path/foo.txt" or die $!;
   }
}
else {
   print "'$path' is not writeable\n";
   eval {
      open my $fh, '>', "$path/foo.txt" or die $!;
      print $fh "foo\n";
      close $fh;
   };
   if ( $@ ) {
      print "\twrite failed: '$@'\n";
   }
   else {
      print "\twrite succeeded\n";
      unlink "$path/foo.txt" or die $!;
   }
}
[download]

- On Mac OS X a user can lock a folder in the Finder Info dialog and '-w $path' will still return true:

perl is_path_writeable.pl folder\ with\ spaces
'folder with spaces/' is writeable
        write failed: 'Operation not permitted at is_path_writeable.pl
+ line 11.
'
[download]

- On Windows '-w $path' will return false for a directory that the user can actually write to:

perl is_path_writeable.pl "C:\Documents and Settings\bke\My Documents"
'C:\Documents and Settings\bke\My Documents' is not writeable
        write succeeded
[download]

I've done some basic google searches and a search of perlmonks but haven't found anything useful regarding -w on windows and Mac.

We try to keep our non-core module prerequisites to a minimum, but am I going to need to resort to platform specific modules to check the path on Mac/Windows?

Or am I better off just attempting to write a file in the $path and check for errors?

Thanks,

Brad Embree

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