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15.5.2.1 Preparing Shell Scripts for Internationalization

Preparing a shell script for internationalization is conceptually similar to the steps described in Sources. The concrete steps for shell scripts are as follows.

  1. Insert the line
              . gettext.sh
    

    near the top of the script. gettext.sh is a shell function library that provides the functions eval_gettext (see eval_gettext Invocation) and eval_ngettext (see eval_ngettext Invocation). You have to ensure that gettext.sh can be found in the PATH.

  2. Set and export the TEXTDOMAIN and TEXTDOMAINDIR environment variables. Usually TEXTDOMAIN is the package or program name, and TEXTDOMAINDIR is the absolute pathname corresponding to $prefix/share/locale, where $prefix is the installation location.
              TEXTDOMAIN=@PACKAGE@
              export TEXTDOMAIN
              TEXTDOMAINDIR=@LOCALEDIR@
              export TEXTDOMAINDIR
    
  3. Prepare the strings for translation, as described in Preparing Strings.
  4. Simplify translatable strings so that they don't contain command substitution ("`...`" or "$(...)"), variable access with defaulting (like ${variable-default}), access to positional arguments (like $0, $1, ...) or highly volatile shell variables (like $?). This can always be done through simple local code restructuring. For example,
              echo "Usage: $0 [OPTION] FILE..."
    

    becomes

              program_name=$0
              echo "Usage: $program_name [OPTION] FILE..."
    

    Similarly,

              echo "Remaining files: `ls | wc -l`"
    

    becomes

              filecount="`ls | wc -l`"
              echo "Remaining files: $filecount"
    
  5. For each translatable string, change the output command ‘echo’ or ‘$echo’ to ‘gettext’ (if the string contains no references to shell variables) or to ‘eval_gettext’ (if it refers to shell variables), followed by a no-argument ‘echo’ command (to account for the terminating newline). Similarly, for cases with plural handling, replace a conditional ‘echo’ command with an invocation of ‘ngettext’ or ‘eval_ngettext’, followed by a no-argument ‘echo’ command.

    When doing this, you also need to add an extra backslash before the dollar sign in references to shell variables, so that the ‘eval_gettext’ function receives the translatable string before the variable values are substituted into it. For example,

              echo "Remaining files: $filecount"
    

    becomes

              eval_gettext "Remaining files: \$filecount"; echo
    

    If the output command is not ‘echo’, you can make it use ‘echo’ nevertheless, through the use of backquotes. However, note that inside backquotes, backslashes must be doubled to be effective (because the backquoting eats one level of backslashes). For example, assuming that ‘error’ is a shell function that signals an error,

              error "file not found: $filename"
    

    is first transformed into

              error "`echo \"file not found: \$filename\"`"
    

    which then becomes

              error "`eval_gettext \"file not found: \\\$filename\"`"