Are wildcards expanded in the shell or the command which the shell forked?

Question

For example, let's assume I have those files in my current work directory:

demo.txt, text.txt, temp.txt, audio.mp3.

When I run this command in the shell:

ls *.txt

What happened under the neath?

Does shell expand it to ls demo.txt text.txt temp.txt first and put it into argv then fork ls?

Or does it do nothing but put ls *.txt directly into argv and then fork ls?

Answer 1

In Linux (and Unix variants in general) wildcard expansion is done by the shell before invoking the command. (Unless explicitly suppressed with quotes.)

In other operating systems (e.g. DOS, Windows) wildcards are always passed verbatim and their expansion is the responsibility of the command.