msgcat(n) Tcl Built-In Commands msgcat(n)______________________________________________________________________________NAMEmsgcat - Tcl message catalog
SYNOPSIS
::msgcat::mc src-string
::msgcat::mclocale ?newLocale?
::msgcat::mcpreferences
::msgcat::mcload dirname
::msgcat::mcset locale src-string ?translate-string?
::msgcat::mcunknown locale src-string
_________________________________________________________________DESCRIPTION
The msgcat package provides a set of functions that can be used to man‐
age 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
Returns a translation of src-string according to the user's cur‐
rent locale. If no translation string exists, ::msgcat::mcun‐
known 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 applicaton can pass the
English string through ::msgcat::mc and use the result. If an applica‐
tion 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::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. The initial locale defaults to the
locale specified in the user's environment. See LOCALE AND
SUBLOCALE 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. If the user has speci‐
fied LANG=en_US_funky, this procedure would return {en_US_funky
en_US en}.
::msgcat::mcload dirname
Searches the specified directory for files that match the lan‐
guage specifications returned by ::msgcat::mcpreferences. Each
file located is sourced. The file extension is ``.msg''. 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. If translate-string is not specified, src-
string is used for both. The function returns translate-string.
::msgcat::mcunknown locale src-string
This routine is called by ::msgcat::mc in the case when a trans‐
lation 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 vaue of ::msgcat::mcunknown is used as the return
vaue for the call to ::msgcat::mc.
LOCALE AND SUBLOCALE SPECIFICATION
The locale is specified by a locale string. 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'' specifes U.S. English.
The locale defaults to the value in env(LANG) at the time the msgcat
package is loaded. If env(LANG) is not defined, then the locale
defaults to ``C''.
When a locale is specified by the user, a ``best match'' search is per‐
formed during string translation. For example, if a user specifies
en_UK_Funky, the locales ``en_UK_Funky'', ``en_UK'', and ``en'' are
searched in order until a matching translation string is found. If no
translation string is available, then ::msgcat::unknown is called.
NAMESPACES AND MESSAGE CATALOGS
Strings stored in the message catalog are stored relative to the names‐
pace 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 typo‐
graphical error.
For example, executing the code
mcset en hello "hello from ::"
namespace eval foo {mcset en hello "hello from ::foo"}
puts [mc hello]
namespace eval foo {puts [mc hello]}
will print
hello from ::
hello from ::foo
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 locale specifier followed by
``.msg''. For example:
es.msg -- spanish
en_UK.msg -- UK English
[3] The file contains a series of calls to mcset, setting the neces‐
sary translation strings for the language. For example:
::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]
POSTITIONAL 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
repositioned. 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 val‐
ues from internationalized strings.
SEE ALSOformat(n), scan(n), namespace(n), package(n)CREDITS
The message catalog code was developed by Mark Harrison.
KEYWORDS
internationalization, i18n, localization, l10n, message, text, transla‐
tion
Tcl 8.1 msgcat(n)
