HPR3722: Bash snippet - plurals in messages

Hacker Public Radio

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