cp and mv behaviour on a busy binary file

[Solène]

Hello,

I found a not coherent behaviour when overwriting a busy binary and I 
would like an explanation on this.
When overwriting a busy binary file, without -f flag, cp won't copy the 
file over the executable while mv will ask if you really want to 
overwrite it.
When using -f, they act the same, the file get overwrited.

Example here :

shell at example : cat test.c
#include <unistd.h>

int main() {
         sleep(1000);
         return 0;
}
shell at example : clang test.c
shell at example : ./a.out &         <- I start the executable
[1] 83540
shell at example : touch file
shell at example : cp file a.out
cp: a.out: Text file busy         <- cp don't agree
shell at example : mv file a.out
override rwxr-xr-x  solene/solene for a.out? (y/n [n]) y <--- mv asks


Kind regards