[:lower:]to support accents and foreign alphabets.
PLATFORM="$(uname -s | tr 'A-Z' 'a-z')"
PLATFORM="$(uname -s | tr '[:upper:]' '[:lower:]')"
a-z are commonly intended to mean "all uppercase" and "all lowercase letters" respectively. This ignores accented characters in English, and foreign characters in other languages:
$ tr 'a-z' 'A-Z' <<< "My fiancée ordered a piña colada." MY FIANCéE ORDERED A PIñA COLADA.
Instead, you can use
[:upper:] to explicitly specify case:
$ tr '[:lower:]' '[:upper:]' <<< "My fiancée ordered a piña colada." MY FIANCÉE ORDERED A PIÑA COLADA.
If you don't want
a-z to match
A-Z to match
Ñ, you can ignore this message.
As of 2019-09-08, BusyBox
tr does not support character classes, so you would have to ignore this message.
Note that the examples used here are multibyte characters in UTF-8. Many implementations (including GNU) fails to deal with them.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.