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