In fixing a new bug recently, I stumbled upon an odd behaviour. When I upload a file via an HTML page, retrieve the file name using CGI, and then call decode_entities on the file name, the result is an empty string. This seems to be Perl version dependent: It fails on Perl v5.20.2 but doesn't fail on v5.10.1. Here is a simple test case:

HTML page: 

<DOCTYPE html>
<HTML>
<BODY>
<form action="filename_entity_test.cgi" method="post" enctype="multipa
+rt/form-data">
Test file name: <input type="file" name="fn">
<br>
<input type="submit" name="submit" value="Upload">
</form>
</BODY>
</HTML>

[download]

CGI code: 

#!/usr/bin/perl -w
use strict;
use CGI qw(:cgi-lib);
use CGI::Carp qw(warningsToBrowser fatalsToBrowser);
use HTML::Entities;

my ($cg, $filename);

$cg = new CGI;

print $cg->header;
print $cg->start_html("Testing decode_entities");

$filename = $cg->param("fn");   

print "Filename before call to decode_entities: $filename<br>\n";

decode_entities($filename);
print "Filename after call to decode_entities: $filename<br>\n";

print $cg->end_html;

[download]

Calling decode_entities with other cgi parameters is successful, and calling it like this: 

$filename = decode_entities($filename);

[download]
is also successful.

In retrospect, I don't really need to worry about entities in the filename, but I'm very curious as to what is going on here.

In reply to CGI Filenames and decode_entities by Marais

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