I will always opt for a readable solution to a one line complex one

how you change input name and get away with it

Awful description, I was like WTF?

Are you on macOS? I suspect that this is a distribution problem. I think macOS has a different echo then GNU/Linux.

echo is a built-in command, so it's the fault of the built-in bash being too old. This should work with newer bash.

Bc If zero or more characters at the beginning of string match the regular expression pattern, return a corresponding match object. Return None if the string does not match the pattern; note that this is different from a zero-length match. So, u get a RE object or None, but we need a bool type as an answer.
You can read more here: https://docs.python.org/3/library/re.html

Is this a GNU extension?

I have exacly the same

I thought this would cause an IndexError or something?

ohhh because strsplit will make double level list .must [[1]] is ok

Hi! What does [[1]] mean please?

So you don't have to convert string literal into std::string?

I got this error "-bash: -1: substring expression < 0", how?

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