Locale::Messages - Gettext Like Message Retrieval
use Locale::Messages (:locale_h :libintl_h); gettext $msgid; dgettext $textdomain, $msgid; dcgettext $textdomain, $msgid, LC_MESSAGES; ngettext $msgid, $msgid_plural, $count; dngettext $textdomain, $msgid, $msgid_plural, $count; dcngettext $textdomain, $msgid, $msgid_plural, $count, LC_MESSAGES; textdomain $textdomain; bindtextdomain $textdomain, $directory; bind_textdomain_codeset $textdomain, $encoding; my $category = LC_CTYPE; my $category = LC_NUMERIC; my $category = LC_TIME; my $category = LC_COLLATE; my $category = LC_MONETARY; my $category = LC_MESSAGES; my $category = LC_ALL;
The module Locale::Messages is a wrapper around the interface to message translation according to the Uniforum approach that is for example used in GNU gettext and Sun's Solaris. It is intended to allow Locale::Messages(3) to switch between different implementations of the lower level libraries but this is not yet implemented.
Normally you should not use this module directly, but the high level interface Locale::TextDomain(3) that provides a much simpler interface. This description is therefore deliberately kept brief. Please refer to the GNU gettext documentation available at http://www.gnu.org/manual/gettext/ for in-depth and background information on the topic.
The lower level module Locale::gettext_pp(3) provides the Perl implementation of gettext() and related functions.
The module exports by default nothing. Every function has to be imported explicitely or via an export tag ("EXPORT TAGS").
Returns the translation for MSGID. Example:
print gettext "Hello World!\n";
If no translation can be found, the unmodified MSGID is returned, i. e. the function can never fail, and will never mess up your original message.
Note for Perl 5.8 and later: The returned string will always have the UTF-8 flag off if the message has been touched, i. e. if it has been translated and if it has been converted to another charset. It will be left untouched in all other cases.
One common mistake is this:
print gettext "Hello $name!";
Perl will interpolate the variable $name before the function will see the string. Unless the corresponding message catalog contains a message "Hello Tom!", "Hello Dick!" or "Hello Harry!", no translation will be found.
$name
Using printf() and friends has its own problems:
print sprintf (gettext ("This is the %s %s."), $color, $thing);
(The example is stupid because neither color nor thing will get translated here ...).
In English the adjective (the color) will precede the noun, many other languages (for example French or Italian) differ here. The translator of the message may therefore have a hard time to find a translation that will still work and not sound stupid in the target language. Many C implementations of printf() allow to change the order of the arguments, and a French translator could then say:
"C'est le %$2s %$1s."
Perl printf() implements this feature as of version 5.8 or better. Consequently you can only use it, if you are sure that your software will run with Perl 5.8 or a later version.
Another disadvantage of using printf() is its cryptic syntax (maybe not for you but translators of your software may have their own opinion).
See the description of the function __x() in Locale::TextDomain(3) for a much better way to get around this problem.
__x()
Like gettext(), but retrieves the message for the specified TEXTDOMAIN instead of the default domain. In case you wonder what a textdomain is, you should really read on with Locale::TextDomain(3).
Like dgettext() but retrieves the message from the specified CATEGORY instead of the default category LC_MESSAGES.
LC_MESSAGES
Retrieves the correct translation for COUNT items. In legacy software you will often find something like:
print "$count file(s) deleted.\n";
or
printf "$count file%s deleted.\n", $count == 1 ? '' : 's';
The first example looks awkward, the second will only work in English and languages with similar plural rules. Before ngettext() was introduced, the best practice for internationalized programs was:
if ($count == 1) { print gettext "One file deleted.\n"; } else { printf gettext "%d files deleted.\n"; }
This is a nuisance for the programmer and often still not sufficient for an adequate translation. Many languages have completely different ideas on numerals. Some (French, Italian, ...) treat 0 and 1 alike, others make no distinction at all (Japanese, Korean, Chinese, ...), others have two or more plural forms (Russian, Latvian, Czech, Polish, ...). The solution is:
printf (ngettext ("One file deleted.\n", "%d files deleted.\n", $count), # argument to ngettext! $count); # argument to printf!
In English, or if no translation can be found, the first argument (MSGID) is picked if $count is one, the second one otherwise. For other languages, the correct plural form (of 1, 2, 3, 4, ...) is automatically picked, too. You don't have to know anything about the plural rules in the target language, ngettext() will take care of that.
$count
This is most of the time sufficient but you will have to prove your creativity in cases like
printf "%d file(s) deleted, and %d file(s) created.\n";
Like ngettext() but retrieves the translation from the specified textdomain instead of the default domain.
Like dngettext() but retrieves the translation from the specified category, instead of the default category LC_MESSAGES.
Sets the default textdomain (initially 'messages').
Binds TEXTDOMAIN to DIRECTORY. Huh? An example:
bindtextdomain "my-package", "./mylocale";
Say, the selected locale (actually the selected locale for category LC_MESSAGES) of the program is 'fr_CH', then the message catalog will be expected in ./mylocale/fr_CH/LC_MESSAGES/my-package.mo.
Sets the output encoding for TEXTDOMAIN to ENCODING.
By default, Locale::Messages will try to load the XS version of the gettext implementation, i. e. Locale::gettext_xs(3) and will fall back to the pure Perl implementation Locale::gettext_pp(3). You can override this behavior by passing the string "gettext_pp" or "gettext_xs" to the function select_package(). Passing "gettext_pp" here, will prefer the pure Perl implementation.
You will normally want to use that in a BEGIN block of your main script.
The function was introduced with libintl-perl version 1.03.
You can (maybe) get the same constants from POSIX(3); see there for a detailed description
This locale category was the reason that these constants from POSIX(3) were included here. Even if it was present in your systems C include file locale.h, it was not provided by POSIX(3). Perl 5.8 and later seems to export the constant if available, although it is not documented in POSIX(3).
Locale::Messages(3) makes an attempt to guess the value of this category for all systems, and assumes the arbitrary value 1729 otherwise.
If you specify the category LC_ALL as the first argument to POSIX::setlocale(), all locale categories will be affected at once.
The module does not export anything unless explicitely requested. You can import groups of functions via two tags:
Imports the functions that are normally defined in the C include file locale.h:
Imports the locale category constants:
A complete example:
1: use Locale::Messages qw (:locale_h :libintl_h); 2: use POSIX qw (setlocale); 3: setlocale (LC_MESSAGES, ''); 4: textdomain ('my-package'); 5: bindtextdomain ('my-package' => '/usr/local/share/locale'); 6: 7: print gettext ("Hello world!\n");
Step by step: Line 1 imports the necessary functions and constants. In line 3 we set the locale for category LC_MESSAGES to the default user settings. For C programs you will often read that LC_ALL is the best category here but this will also change the locale for LC_NUMERIC and many programs will not work reliably after changing that category in Perl; choose your own poison!
In line 4 we say that all messages (translations) without an explicit domain specification should be retrieved from the message catalog for the domain 'my-package'. Line 5 has the effect that the message catalog will be searched under the directory /usr/local/share/locale.
If the user has selected the locale 'fr_CH', and if the file /usr/local/share/locale/fr_CH/LC_MESSAGES/my-package.mo exists, and if it contains a GNU message object file with a translation for the string "Hello world!\n", then line 7 will print the French translation (for Switzerland CH) to STDOUT.
The documentation for GNU gettext explains how to extract translatable strings from your Perl files and how to create message catalogs.
Another less portable example: If your system uses the GNU libc you should be able to find various files with the name libc.mo, the message catalog for the library itself. If you have found these files under /usr/share/locale, then you can try the following:
use Locale::Messages qw (:locale_h :libintl_h); use POSIX qw (setlocale); setlocale LC_MESSAGES, ""; textdomain "libc"; # The following is actually not needed, since this is # one of the default search directories. bindtextdomain libc => '/usr/share/locale'; bind_textdomain_codeset libc => 'iso-8859-1'; print gettext ("No such file or directory");
See Locale::TextDomain(3) for much simpler ways.
Copyright (C) 2002-2003, Guido Flohr <guido@imperia.net>, all rights reserved. See the source code for details.
This software is contributed to the Perl community by Imperia (http://www.imperia.net/).
Locale::TextDomain(3pm), Locale::gettext_pp(3pm), Encode(3pm), perllocale(3pm), POSIX(3pm), perl(1), gettext(1), gettext(3)
2 POD Errors
The following errors were encountered while parsing the POD:
'=item' outside of any '=over'
You forgot a '=back' before '=head1'
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