ar on an existing .a file?

Question

Essentially, what I want to do is this:

gcc foo.c -o foo.o
ar rcs foo.a foo.o
gcc bar.c -o boo.o
ar rcs bar.a bar.o foo.a

I want to archive

Answer 1

ar rcs foo.a foo.o
cp foo.a foo2.a
gcc -c bar.c
ar rs foo2.a bar.o

And perhaps use foo.a instead of foo2.a if you don't need to keep it in its original form.