Overview

Have you ever written a Bash script (or any shell script) where you generate a message like 'Found 42 files' and the day comes when it reports 'Found 1 files'?

Have you been irritated by this? I have, and I go to lengths to deal properly with (English) plurals in my Bash scripts.

Method 1

The simplest solution would be to use an 'if' statement:

if [[ $fcount -eq 1 ]]; then
    echo "Found 1 file"
else
    echo "Found $fcount files"
fi

This works, but to have to do it for every message would be a pain!

Method 2

The next approach to this problem might be to write a Bash function.

pluralise () {
    local singular="${1}"
    local plural="${2}"
    local count="${3}"

    if [[ $count -eq 1 ]]; then
        echo "$singular"
    else
        echo "$plural"
    fi
}

This can be called as follows:

$ i=1; echo "Found $i $(pluralise "file" "files" $i)"
Found 1 file
$ i=42; echo "Found $i $(pluralise "file" "files" $i)"
Found 42 files

The string being displayed with echo contains a command substitution ('$(command)') which returns 'file' or 'files' depending on the value given.

The first two arguments can be more complex than plain strings:

$ i=1; echo "There $(pluralise "is 1 light" "are $i lights" $i)"
There is 1 light
$ i=4; echo "There $(pluralise "is 1 light" "are $i lights" $i)"
There are 4 lights

The pluralise function is available for download.

Method 3

The GNU project has developed a set of utilities called the GNU gettext utilities consisting of tools and documentation for translation. This is a large subject which is not suitable for a short HPR episode such as this one.

Among the tools is 'ngettext' which performs the function we have been discussing - choosing among plural forms. It also implements translations if desired (and translation files are provided as part of the software being developed).

We will not discuss the translation topic here, but the choice of plurals is something that can be used in Bash scripts.

The 'ngettext' tool takes three mandatory parameters:

• MSGID - the singular form of the text
• MSGID-PLURAL - the plural form of the text
• COUNT - the value used to make the singular/plural choice

There are other optional parameters and options but they are not relevant here.

The tool can be used in exactly the same way as the 'pluralise' example above.

$ i=1; echo "There $(ngettext "is 1 light" "are $i lights" $i)"
There is 1 light
$ i=4; echo "There $(ngettext "is 1 light" "are $i lights" $i)"
There are 4 lights

Whether you use this or a Bash function is your choice.

Conclusion

I have been using ngettext in my scripts since I discovered it. If you also need to provide messages in your projects in other languages then this might be a good idea.

I admit that my understanding of the GNU gettext project is superficial, so, on reflection it might be better to use a Bash function, since I don’t currently need all of the features GNU gettext provides.

Links

• The pluralise function. Either add it to the script you’re developing or use the 'source' command to load it.
• GNU gettext utilities, part of the GNU Translation Project.
  • Documentation specific to ngettext