Appendix K. Localization
Localization is an undocumented Bash feature.
A localized shell script echoes its text output in the language defined as the system's locale. A Linux user in Berlin, Germany, would get script output in German, whereas his cousin in Berlin, Maryland, would get output from the same script in English.
To create a localized script, use the following template to write all messages to the user (error messages, prompts, etc.).
#!/bin/bash# localized.sh# Script by St�phane Chazelas,#+ modified by Bruno Haible, bugfixed by Alfredo Pironti.. gettext.shE_CDERROR=65error(){ printf "$@" >&2 exit $E_CDERROR}cd $var || error "`eval_gettext "Can't cd to $var."`" # The triple backslashes (escapes) in front of $var needed#+ "because eval_gettext expects a string#+ where the variable values have not yet been substituted." # -- per Bruno Haibleread -p "`gettext "Enter the value: "`" var# ...# ------------------------------------------------------------------# Alfredo Pironti comments:# This script has been modified to not use the $"..." syntax in#+ favor of the "`gettext "..."`" syntax.# This is ok, but with the new localized.sh program, the commands#+ "bash -D filename" and "bash --dump-po-string filename" #+ will produce no output#+ (because those command are only searching for the $"..." strings)!# The ONLY way to extract strings from the new file is to use the# 'xgettext' program. However, the xgettext program is buggy.# Note that 'xgettext' has another bug.## The shell fragment:# gettext -s "I like Bash" # will be correctly extracted, but . . .# xgettext -s "I like Bash" # . . . fails!# 'xgettext' will extract "-s" because#+ the command only extracts the#+ very first argument after the 'gettext' word.# Escape characters:## To localize a sentence like# echo -e "Helloworld!" #+ you must use# echo -e "`gettext "Helloworld"`" # The "double escape character" before the `t' is needed because#+ 'gettext' will search for a string like: 'Helloworld'# This is because gettext will read one literal `')#+ and will output a string like "Bonjourmonde",#+ so the 'echo' command will display the message correctly.## You may not use# echo "`gettext -e "Helloworld"`" #+ due to the xgettext bug explained above.# Let's localize the following shell fragment:# echo "-h display help and exit" ## First, one could do this:# echo "`gettext "-h display help and exit"`" # This way 'xgettext' will work ok,#+ but the 'gettext' program will read "-h" as an option!## One solution could be# echo "`gettext -- "-h display help and exit"`" # This way 'gettext' will work,#+ but 'xgettext' will extract "--", as referred to above.## The workaround you may use to get this string localized is# echo -e "`gettext " -h display help and exit"`" # We have added a (NULL) at the beginning of the sentence.# This way 'gettext' works correctly, as does 'xgettext.'# Moreover, the NULL character won't change the behavior#+ of the 'echo' command.# ------------------------------------------------------------------ |
bash$ bash -D localized.sh"Can't cd to %s." "Enter the value: " |
This lists all the localized text. (The
-D option lists double-quoted strings prefixed by a
$, without executing the script.)
bash$ bash --dump-po-strings localized.sh#: a:6 msgid "Can't cd to %s." msgstr "" #: a:7 msgid "Enter the value: " msgstr "" |
The
--dump-po-strings option to Bash resembles the
-D option, but uses
gettext "po" format.
| | Bruno Haible points out: Starting with gettext-0.12.2, xgettext -o - localized.sh is recommended instead of bash --dump-po-strings localized.sh, because xgettext . . . 1. understands the gettext and eval_gettext commands (whereas bash --dump-po-strings understands only its deprecated $"..." syntax) 2. can extract comments placed by the programmer, intended to be read by the translator. This shell code is then not specific to Bash any more; it works the same way with Bash 1.x and other /bin/sh implementations. |
Now, build a language.pofile for each language that the script will be translatedinto, specifying the msgstr. AlfredoPironti gives the following example:
fr.po:
#: a:6msgid "Can't cd to $var." msgstr "Impossible de se positionner dans le repertoire $var." #: a:7msgid "Enter the value: " msgstr "Entrez la valeur : " # The string are dumped with the variable names, not with the %s syntax,#+ similar to C programs.#+ This is a very cool feature if the programmer uses#+ variable names that make sense! |
Then, run msgfmt.
msgfmt -o localized.sh.mo fr.po
Place the resulting localized.sh.mo file in the /usr/local/share/locale/fr/LC_MESSAGES directory, and at the beginning of the script, insert the lines:
TEXTDOMAINDIR=/usr/local/share/localeTEXTDOMAIN=localized.sh |
If a user on a French system runs the script, she will get French messages.
| | With older versions of Bash or other shells, localization requires gettext, using the-s option. In this case, the script becomes: #!/bin/bash# localized.shE_CDERROR=65error() { local format=$1 shift printf "$(gettext -s "$format")" "$@" >&2 exit $E_CDERROR}cd $var || error "Can't cd to %s." "$var" read -p "$(gettext -s "Enter the value: ")" var# ... | |
The TEXTDOMAIN andTEXTDOMAINDIR variables need to be set andexported to the environment. This should be done within thescript itself.
---
This appendix written by St�phane Chazelas,with modifications suggested by Alfredo Pironti,and by Bruno Haible, maintainer of GNU gettext.
