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

问题:

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.

回答1:

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.

If you know that your setup is UTF-8 and the terminal will give you the command-line arguments as UTF-8, you can use the A option with Perl's -C switch. This tells your program to assume the arguments are encoded as UTF-8:

% perl -CA program

You also get that with just -C, which turns on several other Unicode options:

% perl -C program

I find "if you know" to be a big red flag that really means "we're not sure", however.

回答2:

Use Encode::Locale:

use Encode::Locale;

decode_argv Encode::FB_CROAK;

This works, also on Win32, pretty OK for me.

回答3:

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

However, this perldoc page suggests that the command line flag -CA should tell it to treat @ARGV as utf-8. (not tested).

回答4:

For example for windows set code

chcp 1251

in perl:

use utf8;
use Modern::Perl;
use Encode::Locale qw(decode_argv);

 if (-t)
{
    binmode(STDIN, ":encoding(console_in)");
    binmode(STDOUT, ":encoding(console_out)");
    binmode(STDERR, ":encoding(console_out)");
}

Encode::Locale::decode_argv();

in command line

perl -C ppixregexplain.pl qr/\bмама\b/i > ex1.html 2>&1  

where ppixregexplain.pl

回答5:

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