Function name valid in bash but not in sh [duplicate]

Question

This question already has an answer here:

• Allowed characters in Linux environment variable names 5 answers

While playing around with bash and sh, I found out that the following is valid in bash:

system.out.println () { printf "$1"; }

but not in sh:

sh: `system.out.println': not a valid identifier

Why would this difference be there? Does the function defined above violate some convention (POSIX etc.) that causes this error?

Answer 1

It's just the dots, you can't use dots in shell function names. Or any variable name, for that matter.

I'll link you to this question: Allowed characters in linux environment variable names