msgcat(1T)						       Tcl Bundled Packages							msgcat(1T)

__________________________________________________________________________________________________________________________________________________

NAME

       msgcat - Tcl message catalog

SYNOPSIS

       package require Tcl 8.2

       package require msgcat 1.3.4

       ::msgcat::mc src-string ?arg arg ...?

       ::msgcat::mcmax ?src-string src-string ...?

       ::msgcat::mclocale ?newLocale?

       ::msgcat::mcpreferences

       ::msgcat::mcload dirname

       ::msgcat::mcset locale src-string ?translate-string?

       ::msgcat::mcmset locale src-trans-list

       ::msgcat::mcunknown locale src-string
_________________________________________________________________

DESCRIPTION

       The  msgcat  package  provides  a set of functions that can be used to manage multi-lingual user interfaces.  Text strings are defined in a
       ``message catalog'' which is independent from the application, and which can be edited  or  localized  without  modifying  the  application
       source code.  New languages or locales are provided by adding a new file to the message catalog.

       Use  of the message catalog is optional by any application or package, but is encouraged if the application or package wishes to be enabled
       for multi-lingual applications.

COMMANDS

       ::msgcat::mc src-string ?arg arg ...?
	      Returns a translation of src-string according to the user's current locale.  If additional arguments past src-string are given,  the
	      format command is used to substitute the additional arguments in the translation of src-string.

       ::msgcat::mc will search the messages defined in the current namespace for a translation of src-string; if none is found, it will search in
       the parent of the current namespace, and so on until it reaches the global namespace.  If no translation string exists, ::msgcat::mcunknown
       is called and the string returned from ::msgcat::mcunknown is returned.

       ::msgcat::mc  is  the  main function used to localize an application.  Instead of using an English string directly, an application can pass
       the English string through ::msgcat::mc and use the result.  If an application is written for a single language in this fashion, then it is
       easy to add support for additional languages later simply by defining new message catalog entries.

       ::msgcat::mcmax ?src-string src-string ...?
	      Given  several  source  strings, ::msgcat::mcmax returns the length of the longest translated string.  This is useful when designing
	      localized GUIs, which may require that all buttons, for example, be a fixed width (which will be the width of the widest button).

       ::msgcat::mclocale ?newLocale?
	      This function sets the locale to newLocale.  If newLocale is omitted, the current locale is returned, otherwise the  current  locale
	      is  set  to  newLocale.	msgcat stores and compares the locale in a case-insensitive manner, and returns locales in lowercase.  The
	      initial locale is determined by the locale specified in the user's environment.  See LOCALE SPECIFICATION below for a description of
	      the locale string format.

       ::msgcat::mcpreferences
	      Returns  an ordered list of the locales preferred by the user, based on the user's language specification.  The list is ordered from
	      most specific to least preference.  The list is derived from the current locale set in msgcat by ::msgcat::mclocale, and	cannot	be
	      set independently.  For example, if the current locale is en_US_funky, then ::msgcat::mcpreferences returns {en_US_funky en_US en}.

       ::msgcat::mcload dirname
	      Searches	the  specified	directory  for files that match the language specifications returned by ::msgcat::mcpreferences (note that
	      these are all lowercase), extended by the file extension ``.msg''.  Each matching file is read in order, assuming a UTF-8  encoding.
	      The  file contents are then evaluated as a Tcl script.  This means that Unicode characters may be present in the message file either
	      directly in their UTF-8 encoded form, or by use of the backslash-u quoting recognized by Tcl  evaluation.   The  number  of  message
	      files which matched the specification and were loaded is returned.

       ::msgcat::mcset locale src-string ?translate-string?
	      Sets  the  translation for src-string to translate-string in the specified locale and the current namespace.  If translate-string is
	      not specified, src-string is used for both.  The function returns translate-string.

       ::msgcat::mcmset locale src-trans-list
	      Sets the translation for multiple source strings in src-trans-list in the specified locale and the  current  namespace.	src-trans-
	      list  must have an even number of elements and is in the form {src-string translate-string ?src-string translate-string ...?} ::msg-
	      cat::mcmset can be significantly faster than multiple invocations of ::msgcat::mcset. The function returns the  number  of  transla-
	      tions set.

       ::msgcat::mcunknown locale src-string
	      This  routine  is  called  by  ::msgcat::mc in the case when a translation for src-string is not defined in the current locale.  The
	      default action is to return src-string.  This procedure can be redefined by the application, for example to log error  messages  for
	      each  unknown  string.   The  ::msgcat::mcunknown  procedure  is invoked at the same stack context as the call to ::msgcat::mc.  The
	      return value of ::msgcat::mcunknown is used as the return value for the call to ::msgcat::mc.

LOCALE SPECIFICATION

       The locale is specified to msgcat by a locale string passed to ::msgcat::mclocale.  The locale string  consists	of  a  language  code,	an
       optional  country  code,  and  an  optional system-specific code, each separated by ``_''.  The country and language codes are specified in
       standards ISO-639 and ISO-3166.	For example, the locale ``en'' specifies English and ``en_US'' specifies U.S. English.

       When the msgcat package is first loaded, the locale is initialized  according  to  the  user's  environment.   The  variables  env(LC_ALL),
       env(LC_MESSAGES),  and  env(LANG)  are  examined  in  order.   The first of them to have a non-empty value is used to determine the initial
       locale.	The value is parsed according to the XPG4 pattern
	      language[_country][.codeset][@modifier]
       to extract its parts.  The initial locale is then set by calling ::msgcat::mclocale with the argument
	      language[_country][_modifier]
       On Windows, if none of those environment variables is set, msgcat will attempt to extract locale information from  the  registry.   If  all
       these attempts to discover an initial locale from the user's environment fail, msgcat defaults to an initial locale of ``C''.

       When  a	locale is specified by the user, a ``best match'' search is performed during string translation.  For example, if a user specifies
       en_GB_Funky, the locales ``en_GB_Funky'', ``en_GB'', and ``en'' are searched in order until a matching translation string is found.  If	no
       translation string is available, then ::msgcat::mcunknown is called.

NAMESPACES AND MESSAGE CATALOGS

       Strings	stored	in  the message catalog are stored relative to the namespace from which they were added.  This allows multiple packages to
       use the same strings without fear of collisions with other packages.  It also allows the source string to be  shorter  and  less  prone	to
       typographical error.

       For example, executing the code
	      ::msgcat::mcset en hello "hello from ::"
	      namespace eval foo {
		 ::msgcat::mcset en hello "hello from ::foo"
	      }
	      puts [::msgcat::mc hello]
	      namespace eval foo {puts [::msgcat::mc hello]}
       will print
	      hello from ::
	      hello from ::foo

       When  searching for a translation of a message, the message catalog will search first the current namespace, then the parent of the current
       namespace, and so on until the global namespace is reached.  This allows child namespaces to "inherit" messages from  their  parent  names-
       pace.

       For example, executing (in the ``en'' locale) the code
	      ::msgcat::mcset en m1 ":: message1"
	      ::msgcat::mcset en m2 ":: message2"
	      ::msgcat::mcset en m3 ":: message3"
	      namespace eval ::foo {
		 ::msgcat::mcset en m2 "::foo message2"
		 ::msgcat::mcset en m3 "::foo message3"
	      }
	      namespace eval ::foo::bar {
		 ::msgcat::mcset en m3 "::foo::bar message3"
	      }
	      namespace import ::msgcat::mc
	      puts "[mc m1]; [mc m2]; [mc m3]"
	      namespace eval ::foo {puts "[mc m1]; [mc m2]; [mc m3]"}
	      namespace eval ::foo::bar {puts "[mc m1]; [mc m2]; [mc m3]"}
       will print
	      :: message1; :: message2; :: message3
	      :: message1; ::foo message2; ::foo message3
	      :: message1; ::foo message2; ::foo::bar message3

LOCATION AND FORMAT OF MESSAGE FILES

       Message files can be located in any directory, subject to the following conditions:

       [1]    All message files for a package are in the same directory.

       [2]    The message file name is a msgcat locale specifier (all lowercase) followed by ``.msg''.	For example:
	      es.msg	-- spanish
	      en_gb.msg -- United Kingdom English

       [3]    The file contains a series of calls to mcset and mcmset, setting the necessary translation strings for the language, likely enclosed
	      in a namespace eval so that all source strings are tied to the namespace of the package. For example, a short es.msg might contain:
	      namespace eval ::mypackage {
		 ::msgcat::mcset es "Free Beer!" "Cerveza Gracias!"
	      }

RECOMMENDED MESSAGE SETUP FOR PACKAGES

       If a package is installed into a subdirectory of the tcl_pkgPath and loaded via package require, the following procedure is recommended.

       [1]    During package installation, create a subdirectory msgs under your package directory.

       [2]    Copy your *.msg files into that directory.

       [3]
	       Add the following command to your package initialization script:
	      # load language files, stored in msgs subdirectory
	      ::msgcat::mcload [file join [file dirname [info script]] msgs]

POSITIONAL CODES FOR FORMAT AND SCAN COMMANDS

       It is possible that a message string used as an argument to format might have positionally dependent parameters that might need to be repo-
       sitioned.  For example, it might be syntactically desirable to rearrange the sentence structure while translating.
	      format "We produced %d units in location %s" $num $city
	      format "In location %s we produced %d units" $city $num

       This can be handled by using the positional parameters:
	      format "We produced %1$d units in location %2$s" $num $city
	      format "In location %2$s we produced %1$d units" $num $city

       Similarly, positional parameters can be used with scan to extract values from internationalized strings.

CREDITS

       The message catalog code was developed by Mark Harrison.

SEE ALSO

       format(1T), scan(1T), namespace(1T), package(1T)

KEYWORDS

       internationalization, i18n, localization, l10n, message, text, translation

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +--------------------+-----------------+
       |  ATTRIBUTE TYPE    | ATTRIBUTE VALUE |
       +--------------------+-----------------+
       |Availability	    | SUNWTcl	      |
       +--------------------+-----------------+
       |Interface Stability | Uncommitted     |
       +--------------------+-----------------+
NOTES

       Source for Tcl is available on http://opensolaris.org.

msgcat									1.3								msgcat(1T)