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Locale::XGettext(3pm) User Contributed Perl Documentation Locale::XGettext(3pm)

Locale::XGettext - Extract Strings To PO Files

    use base 'Locale::XGettext';

Locale::XGettext is the base class for various string extractors. These string extractors can be used as standalone programs on the command-line or as a module as a part of other software.

See <https://github.com/gflohr/Locale-XGettext> for an overall picture of the software.

This section describes the usage of extractors based on this library. See "SUBCLASSING" and the sections following it for the API documentation!

    xgettext-LANG [OPTIONS] [INPUTFILE]...

LANG will be replaced by an identifier for the language that a specific extractor was written for, for example "xgettext-txt" for plain text files or "xgettext-tt2" for templates for the Template Toolkit version 2 (see Template).

By default, string extractors based on this module extract strings from one or more INPUTFILES and write the output to a file "messages.po" if any strings had been found.

The command line options are mostly compatible to xgettext from GNU Gettext <https://www.gnu.org/software/gettext/manual/html_node/xgettext-Invocation.html>.

INPUT FILE LOCATION

All non-option arguments are interpreted as input files containing strings to be extracted. If the input file is "-", standard input is read.
Read the names of the input files from FILE instead of getting them from the command line.

Note! Unlike xgettext from GNU Gettext, extractors based on Locale::XGettext accept this option multiple times, so that you can read the list of input files from multiple files.

Add DIRECTORY to the list of directories. Source files are searched relative to this list of directories. The resulting .po file will be written relative to the current directory, though.

OUTPUT FILE LOCATION

Use NAME.po for output (instead of messages.po).
Write output to specified FILE (instead of NAME.po or messages.po).
Output files will be placed in directory DIR.

If the output file is - or /dev/stdout, the output is written to standard output.

INPUT FILE INTERPRETATION

Specifies the encoding of the input files. This option is needed only if some untranslated message strings or their corresponding comments contain non-ASCII characters.

By default the input files are assumed to be in ASCII.

Note! Some extractors have a fixed input set, UTF-8 most of the times.

OPERATION MODE

Join messages with existing files. This is a shortcut for adding the output file to the list of input files. The output file is read, and then all messages from other input files are added.

For obvious reasons, you cannot use this option if output is written to standard output.

PO entries that are present in FILE.po are not extracted.
Place comment blocks starting with TAG in the output if they precede a keyword line.
Place all comment blocks that precede a keyword line in the output.

Extract all strings, not just the ones marked with keywords.

Not all extractors support this option!

Use WORD as an additional keyword.

Not all extractors support this option!

Do not use default keywords! If you define your own keywords, you use usually give the option '--keyword' first without an argument to reset the keyword list to empty, and then you give a '--keyword' option for everyt keyword wanted.

Not all extractors support this option!

Original explanation from GNU gettext:

Specifies additional flags for strings occurring as part of the argth argument of the function word. The possible flags are the possible format string indicators, such as Xc-formatX, and their negations, such as Xno-c-formatX, possibly prefixed with Xpass-X.

The meaning of --flag=function:arg:lang-format is that in language lang, the specified function expects as argth argument a format string. (For those of you familiar with GCC function attributes, --flag=function:arg:c-format is roughly equivalent to the declaration X__attribute__ ((__format__ (__printf__, arg, ...)))X attached to function in a C source file.) For example, if you use the XerrorX function from GNU libc, you can specify its behaviour through --flag=error:3:c-format. The effect of this specification is that xgettext will mark as format strings all gettext invocations that occur as argth argument of function. This is useful when such strings contain no format string directives: together with the checks done by Xmsgfmt -cX it will ensure that translators cannot accidentally use format string directives that would lead to a crash at runtime.

The meaning of --flag=function:arg:pass-lang-format is that in language lang, if the function call occurs in a position that must yield a format string, then its argth argument must yield a format string of the same type as well. (If you know GCC function attributes, the --flag=function:arg:pass-c-format option is roughly equivalent to the declaration X__attribute__ ((__format_arg__ (arg)))X attached to function in a C source file.) For example, if you use the X_X shortcut for the gettext function, you should use --flag=_:1:pass-c-format. The effect of this specification is that xgettext will propagate a format string requirement for a _("string") call to its first argument, the literal "string", and thus mark it as a format string. This is useful when such strings contain no format string directives: together with the checks done by Xmsgfmt -cX it will ensure that translators cannot accidentally use format string directives that would lead to a crash at runtime.

Note that Locale::XGettext ignores the prefix pass- and therefore most extractors based on Locale::XGettext will also ignore it.

Individual extractors may define more language-specific options.

Write PO file even if empty. Normally, empty PO files are not written, and existing output files are not overwritten if they would be empty.
Do not write '#: filename:line' lines into the output PO files.
Generate '#: filename:line' lines in the output PO files. This is the default.
Sort output entries alphanumerically.
Sort output entries by source file location.
Do not write header with meta information. The meta information is normally included as the "translation" for the empty string.

If you want to hava a translation for an empty string you should also consider using message contexts.

Set the copyright holder to STRING in the output PO file.
Omit FSF copyright in output for foreign user.
Set package name in output
Set package version in output.
Set report address for msgid bugs.
Use STRING or "" as prefix for msgstr values.
Use STRING or "" as suffix for msgstr values.

INFORMATIVE OUTPUT

Display short help and exit.
Output version information and exit.

Writing a complete extractor script in Perl with Locale::XGettext is as simple as:

    #! /usr/bin/env perl
    use Locale::Messages qw(setlocale LC_MESSAGES);
    use Locale::TextDomain qw(YOURTEXTDOMAIN);
    use Locale::XGettext::YOURSUBCLASS;
    Locale::Messages::setlocale(LC_MESSAGES, "");
    Locale::XGettext::YOURSUBCLASS->newFromArgv(\@ARGV)->run->output;

Writing the extractor class is also trivial:

    package Locale::XGettext::YOURSUBCLASS;
    use base 'Locale::XGettext';
    sub readFile {
        my ($self, $filename) = @_;
        foreach my $found (search_for_strings_in $filename) {
            $self->addEntry({
                msgid => $found->{string},
                # More possible fields following, see 
                # addEntry() below!
            }, $found->{possible_comment});
        }
        # The return value is actually ignored.
        return $self;
    }

All the heavy lifting happens in the method readFile() that you have to implement yourself. All other methods are optional.

See the section "METHODS" below for information on how to additionally modify the behavior your extractor.

OPTIONS is a hash reference containing the above command-line options but with every hyphen replaced by an underscore. You should normally not use this constructor!
ARGV is a reference to a an array of command-line arguments that is passed verbatim to Getopt::Long::GetOptionsFromArray. After processing all options and arguments, the constructor new() above is then invoked with the cooked command-line arguments.

This is the constructor that you should normally use in custom extractors that you write.

Locale::XGettext is an abstract base class. All public methods may be overridden by subclassed extractors.

You have to implement this method yourself. In it, read FILENAME, extract all relevant entries, and call addEntry() for each entry found.

The method is not invoked for filenames ending in ".po" or ".pot"! For those files, readPO() is invoked instead.

This method is the only one that you have to implement!

You should invoke this method for every entry found.

COMMENT is an optional comment that you may have extracted along with the message. Note that addEntry() checks whether this comment should make it into the output. Therefore, just pass any comment that you have found preceding the keyword.

ENTRY should be a reference to a hash with these possible keys:

The entry's message id.
A possible plural form.
A possible message context.
A source reference in the form "FILENAME: LINENO".
Set a flag for this entry, for example "perl-brace-format" or "no-perl-brace-format". You can comma-separate multiple flags.
The keyword that triggered the entry. If you set this property and the keyword definition contained an automatic comment, the comment will be added. You can try this out like this: 

    xgettext-my.pl --keyword=greet:1,'"Hello, world!"'

If you set keyword to "greet", the comment "Hello, world" will be added. Note that the "double quotes" are part of the command-line argument!

Likewise, if "--flag" was specified on the command-line or the extractor ships with default flags, entries matching the flag definition will automatically have this flag.

You can try this out with:

    xgettext-my.pl --keyword="greet:1" --flag=greet:1:hello-format

Now all PO entries for the keyword "greet" will have the flag "hello-format"

True if the entry is fuzzy. There is no reason to use this in string extractors because they typically product .pot files without translations.
Sets an automatic comment, not recommended. Rather set the keyword (see above) and let Locale::XGettext set the comment as appropriate.

Instead of a hash you can currently also pass a Locale::PO object. This may no longer be supported in the future. Do not use!

Return a hash reference with all keyword definitions as Locale::XGettext::Util::Keyword objects.
Return a reference to an array with all keyword definitions as option strings suitable for the command-line option "--keyword".
Return an array reference with all flag definitions as Locale::XGettext::Util::Flag objects.
Return a reference to an array with all flag definitions as option strings suitable for the command-line option "--flag".
Get all command-line options as a hash reference.
Get the value for command line option OPTION.
Set the value for command line option OPTION to VALUE.
The default representation returns nothing.

Your own implementation can return an reference to an array of arrays, each of them containing one option specification consisting of four items:

  • The option specification for Getopt::Long(3pm), for example "f|filename=s" for an option expecting a mandatory string argument.
  • The name of the option. This is what gets passed to option() above. It should generally be the long option name with hyphens converted to underscores.
  • The option description for the usage information, for example "-f, --files=STRING" for options taking arguments or something like " --verbose" for long-only options. This is printed in the left column, when you invoke your extractor with "--help".
  • The description of this option. This is printed in the right column, when you invoke your extractor with "--help".
Prints all language-specific options to standard output, calls languageSpecificOptions() internally. This is used for the output for the option "--help".
Returns nothing by default. You can return a string describing the expected input format, when invoked with "--help".
Returns nothing by default. You can return a string that is printed, when invoked with "--version".
Returns nothing by default. You can return a string describing the bug tracking address, when invoked with "--help".
Returns false by default. Return a truthy value if your extractor supports the option "--extract-all".
Returns true by default. Return a false value if your extractor does not support the option "--keyword".
Returns true by default. Return a false value if your extractor does not support the option "--flag".
Returns true by default. Return a false value if your extractor does not support input from files. In this case you should implement readFromNonFiles().
Return the name of the program for usage and help information. Defaults to just $0 but you can return another value here.
Runs the extractor once. The default implementation scans all input sources for translatable strings and collects them.
Print the output as a PO file to the specified output location.
This method is invoked after all input files have been processed. The default implementation does nothing. You may use the method for extracting strings from additional sources like a database.
Given an input filename FILENAME the method returns the absolute location of the file. The default implementation honors the option "-D, --directory".
Returns a reference to an empty array.

Subclasses may return a reference to an array with default keyword definitions for the specific language. The default keywords (actually just a subset for it) for the language C would look like this (expressed in JSON):

    [
        "gettext:1",
        "ngettext:1,2",
        "pgettext:1c,2",
        "npgettext:1c,2,3"
    ]

See above the description of the command-line option "--keyword" for more information about the meaning of these strings.

Returns a reference to an empty array.

Subclasses may return a reference to an array with default flag specifications for the specific language. An example may look like this (expressed in JSON):

    [
        "gettextx:1:perl-brace-format",
        "ngettextx:1:perl-brace-format",
        "ngettextx:2:perl-brace-format",
    ]

We assume that "gettextx()" and "gettextx() are keywords for the language in question. The above default flag definition would mean that in all invocations of the function "gettextx()", the 1st argument would get the flag "perl-brace-format". In all invocations of "ngettextx()", the 1st and 2nd argument would get the flag "perl-brace-format".

You can prefix the format with "no-" which tells the GNU gettext tools that the particular never uses that format.

You can additionally prefix the format with "pass-" but this is ignored by Locale::XGettext. If you want to implemnt the GNU xgettext behavior for the "pass-" prefix, you have to implement it yourself in your extractor.

Gets invoked for every PO entry but after it has been promoted to a Locale::PO(3pm) object. The implementation of this method is likely to be changed in the future.

Do not use!

Reads FILENAME as .po or .pot file. There is no reason why you should override or invoke this method.
Returns a list of PO entries represented by hash references. Do not use or override this method!
Prints the help for language-specific options. Override it, if you are not happy with the formatting.

Copyright (C) 2016-2017 Guido Flohr <guido.flohr@cantanea.com>, all rights reserved.

Getopt::Long, xgettext(1), perl

2023-02-05 perl v5.36.0