Shell – Separate namespaces for functions and variables in POSIX shells

dashposixshell

In dash, functions and variables appear to live in separate namespaces:

fn(){
    fn="hello world"
}
fn; echo "The value is $fn!" #prints: The value is hello world!
fn; echo "The value is $fn!" #prints: The value is hello world!
#the fn variable doesn't conflict with the fn function

Is this a dash-specific feature or a POSIX guarantee?

Best Answer

A guarantee:

2.9.5 Function Definition Command

A function is a user-defined name that is used as a simple command to call a compound command with new positional parameters. A function is defined with a "function definition command". [...]

The function is named fname; the application shall ensure that it is a name (see XBD Name) and that it is not the name of a special built-in utility. An implementation may allow other characters in a function name as an extension. The implementation shall maintain separate name spaces for functions and variables.

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