bash localization won't work with multilines strings (with strong syntax or through `eval`)

Question

There is a nice feature in bash, about localization (language translation):

TEXTDOMAIN=coreutils
LANG=fr_CH.utf8
echo $"system boot"
démarrage système

(Nota: For this work, fr_CH.utf8 was already generated on your system... Else you may try with your own locale... or install locales and generate one.)

The problem:

But if this work fine with simple strings, when string contain a \n (or worst: a backtick ` things are more complicated:

echo $"Written by %s, %s, %s,\nand %s.\n"
Written by %s, %s, %s,\nand %s.\n

This is not attended answer.

(Nota2: For this work, exact message has to be prepared in .mo message file, in this sample/test, I use existant coreutils.mo files, which could be unformated with the command msgunfmt.)

At all, the only way I've found to do the translation is:

eval echo \$\"$'Written by %s, %s, %s,\nand %s.\n'\"
Écrit par %s, %s, %s,
et %s.

or

msg=$'Written by %s, %s, %s,\nand %s.\n'
eval echo \$\""$msg"\"
Écrit par %s, %s, %s,
et %s.

(You could see two double quotes... not very sexy...)

And finally I could:

WRITTERS=(Hans Pierre Jackob Heliott)
eval printf \$\""$msg"\" ${WRITTERS[@]}
Écrit par Hans, Pierre, Jackob,
et Heliott.

But as I've heard recently that eval is evil... ;-)

In fact, I don't have problem with an eval that's run with only hard coded part, but I would appreciate a way to keep this eval out and to write this kind of part in a more natural or readable manner.

At all @techno 's answer let me see that my first idea is something dangerous as if WRITTERS contain some ;ls, for sample...

Edit: So question is:

How could I keep this eval out and/or write this in a more sexy fashion

Nota:

$ printf "I use bash %s on Debian %s\n" $BASH_VERSION $(</etc/debian_version)
I use bash 4.1.5(1)-release on Debian 6.0.6

Answer 1

I've played a little bit with this feature and this is what I came up with: you can include the newline verbatim as:

$ echo $"Written by %s.
> "
Écrit par %s.
$ 

In a script:

#!/bin/bash

message=$"Written by %s.
"

printf "$message" Gniourf

This script will output:

Écrit par Gniourf.

Ok, this is not really an answer, but it might help a little bit (at least, we're not using the evil eval).

Personal remark: I find this feature really clunky!

Answer 2

If using eval is bad with arbitrary variables, there is a way to do this only when called/needed, in running eval only on message part:

function lPrintf() {
    local sFormat="$(
        eval 'echo $"'"${1}"'"'.
    )"
    shift
    printf "${sFormat%.}" $@
}

lPrintf "system boot"
démarrage système

lPrintf  $'Written by %s, %s, %s,\nand %s.\n' techno moi lui-même bibi
Écrit par techno, moi, lui-même,
et bibi.

( The dot at end of translated string ensure that whole string, including leading line-break, where passed to variable sFormat. They will be dropped with ${sFormat%.} )

Answer 3

OK I think finally got it right.

iprintf() {
    msg="$2"
    domain="$1"
    shift
    shift
    imsg=$(gettext -ed "$domain" "$msg" ; echo EOF)
    imsg="${imsg%EOF}"
    printf "$imsg" "$@"
}

Usage example:

LANG=fr_CH.utf8 iprintf coreutils "If FILE is not specified, use %s.  %s as FILE is common.\n\n" foo bar

Answer 4

Simple solution for building a translation function:

f() {
    eval 'local msg=$"'"${1//[\"\$\`]}"\"
    shift
    printf "${msg}" "$@"
}

Test:

TEXTDOMAIN=coreutils
LANG="fr_CH.utf8"
f system boot
démarrage système

f $'Written by %s, %s, %s,\nand %s.\n' Athos Portos Aramis Shreck
Écrit par Athos, Portos, Aramis
et Shreck.

But as I prefer setting variables instead of forking function:

f() {
    eval 'local msg=$"'"${1//[\"\$\`]}"\"
    local -n variable=$2
    shift 2
    printf -v variable "$msg" "$@"
}

Then

f $'Written by %s, %s, %s,\nand %s.\n' string Huey Dewey Louie Batman
echo ${string@Q}
$'Écrit par Huey, Dewey, Louie\net Batman.\n'

echo "$string"
Écrit par Huey, Dewey, Louie
et Batman.

Or even better as a full translation function:

f() {
    local store=false OPTIND OPTARG OPTERR varname
    while getopts 'd:v:' opt ;do
        case $opt in
            d ) local TEXTDOMAIN=$OPTARG ;;
            v ) varname=$OPTARG ;;
        esac
    done
    shift $((OPTIND-1))
    eval 'local msg=$"'"${1//[\"\$\`]}"\"
    shift
    printf ${varname+-v} $varname "$msg" "$@"
}

Then

f -d libc -v string "Permission denied"
echo $string
Permission non accordée

f -d coreutils $'Written by %s, %s, %s,\nand %s.\n' Riri Fifi Loulou Georges
Écrit par Riri, Fifi, Loulou
et Georges.

Old answer (Jan 2013)

Well, there is my self answer:

This seem not well implemented now. Work in many situations, but, while

echo "$(gettext 'missing character class name `[::]'\')"
caractère de nom de classe « [::] » manquant

work simply, the same string seem impossible to translate using this bashism:

echo $"missing character class name `[::]'"
> 

the console stay locked (waiting for such an end of string) adding ``" ` would immerse bash in a complex interpretation process :->>

> `"
bash: command substitution: line 1: Caractère de fin de fichier (EOF) prématuré lors de la recherche du « ' » correspondant
bash: command substitution: line 2: Erreur de syntaxe : fin de fichier prématurée
missing character class name 

And, of course:

echo $"missing character class name \`[::]'"
missing character class name `[::]'

make no translation. :-p

While translating this string containing two backticks work finely:

echo $"%s}: integer required between `{' and `}'"
%s} : entier requis entre « { » et « } »

There is a script where you may see some of mine unsuccessfull trys.

#!/bin/bash

echo "Localized tests"
export TEXTDOMAIN=coreutils
export LANG=fr_CH.UTF-8
export WRITTERS=(Athos Portos Aramis Dartagnan\ Le\ Beau)

echo '#First method# whitout eval'

declare -A MyMessages;
MyMessages[sysReboot]=$"system boot"
MyMessages[writtenBy]=$"Written by %s, %s, %s,
and %s.
"
MyMessages[intReq]=$"%s}: integer required between `{' and `}'"
MyMessages[trClass]=$"when translating, the only character classes that may appear in
string2 are `upper' and `lower'"
# MyMessages[missClass]=$"missing character class name `[::]'" 

for msgIdx in ${!MyMessages[@]} ;do
    printf "\n--- Test chain '%s' ---\n" $msgIdx
    case $msgIdx in
    writ* )
        printf "${MyMessages[$msgIdx]}\n" "${WRITTERS[@]}"
        ;;
    intReq )
        printf "ARRAY{${MyMessages[$msgIdx]}\n" NaN
        ;;
    * )
        printf "${MyMessages[$msgIdx]}\n"
        ;;
    esac
  done

echo $'###\n#Second method# whith limited eval'
unset MyMessages;

declare -A MyMessages;

lPrintf() {
    local sFormat="$(
        eval 'echo $"'"${1}"'"'.
    )"
    shift
    printf "${sFormat%.}" "$@"
}

MyMessages[sysReboot]="system boot"
MyMessages[writtenBy]=$'Written by %s, %s, %s,\nand %s.\n'
MyMessages[intReq]="%s}: integer required between \`{' and \`}'"
MyMessages[trClass]="when translating, the only character classes that "
MyMessages[trClass]+=$'may appear in\nstring2 '
MyMessages[trClass]+="are \`upper' and \`lower'"
MyMessages[missClass]="missing character class name \`[::]'"

for msgIdx in ${!MyMessages[@]} ;do
    printf "\n--- Test chain '%s' ---\n" $msgIdx
    case $msgIdx in
    writ* )
        lPrintf "${MyMessages[$msgIdx]}" "${WRITTERS[@]}"
        ;;
    intReq )
        lPrintf "${MyMessages[$msgIdx]}" NaN
        ;;
    * )
        lPrintf "${MyMessages[$msgIdx]}"
        ;;
    esac
  done

and his output:

Localized tests
#First method# whitout eval

--- Test chain 'trClass' ---
à la traduction, les seules classes de caractères qui peuvent apparaître
dans string2 sont « upper » ou « lower »

--- Test chain 'intReq' ---
ARRAY{NaN} : entier requis entre « { » et « } »

--- Test chain 'sysReboot' ---
démarrage système

--- Test chain 'writtenBy' ---
Écrit par Athos, Portos, Aramis,
et Dartagnan Le Beau.

###
#Second method# whith limited eval

--- Test chain 'trClass' ---
à la traduction, les seules classes de caractères qui peuvent apparaître
dans string2 sont « upper » ou « lower »
--- Test chain 'missClass' ---
./localized.sh: eval: line 44: Caractère de fin de fichier (EOF) prématuré lors de la recherche du « ` » correspondant
./localized.sh: eval: line 45: Erreur de syntaxe : fin de fichier prématurée

--- Test chain 'intReq' ---
NaN} : entier requis entre « { » et « } »
--- Test chain 'sysReboot' ---
démarrage système
--- Test chain 'writtenBy' ---
Écrit par Athos, Portos, Aramis,
et Dartagnan Le Beau.

If anyone could help my to remove comments and/or error message in this script!? ... (in less then 8 hours?!)

At all, thanks to everyone. (My bounty will go to @gniourf_gniourf unless best answer in 8 hours. But thanks to @techno too, I like your lPrintf! )