How can I treat command-line arguments as UTF-8 in Perl?

Question

How do I treat the elements of @ARGV as UTF-8 in Perl?

Currently I'm using the following work-around ..

use Encode qw(decode encode);

my $foo = $ARGV[0];
$foo = decode("utf-8", $foo);

.. which works but is not very elegant.

I'm using Perl v5.8.8 which is being called from bash v3.2.25 with a LANG set to en_US.UTF-8.

Answer 1

You shouldn't have to do anything special to the string. Perl strings are in UTF-8 by default starting with Perl 5.8.

perl -CO -le 'print "\x{2603}"' | xargs perl -le 'print "I saw @ARGV"'

The code above works just fine on Ubuntu 9.04, OS X 10.6, and FreeBSD 7.

FalseVinylShrub brings up a good point, We can see a definite difference between

perl -Mutf8 -wle ';print utf8::is_utf8($ARGV[0]) ? "t" : "f"' a

and

perl -Mutf8 -CA -wle ';print utf8::is_utf8($ARGV[0]) ? "t" : "f"' a

Answer 2

The way you've done it seems correct. That's what I would do.

However, this perldoc page http://perldoc.perl.org/perlrun.html#*-C-[number/list]* suggests that the command line flag -CA should tell it to treat @ARGV as utf-8. (not tested).

Answer 3

Outside data sources are tricky in Perl. For command-line arguments, you're probably getting them as the encoding specified in your locale. Don't rely on your locale to be the same as someone else who might run your program.

You have to find out what that is then convert to Perl's internal format. Fortunately, it's not that hard.

The I18N::Langinfo module has the stuff you need to get the encoding:

    use I18N::Langinfo qw(langinfo CODESET);
    my $codeset = langinfo(CODESET);

Once you know the encoding, you can decode them to Perl strings:

    use Encode qw(decode);
    @ARGV = map { decode $codeset, $_ } @ARGV;

Although Perl encodes internal strings as UTF-8, you shouldn't ever think or know about that. You just decode whatever you get, which turns it into Perl's internal representation for you. Trust that Perl will handle everything else. When you need to store the data, ensure that you use the encoding you like.