touch lib.h queue.h queue.c lib.c
echo "void main() {}" | tee main.c > queue_test.c
This will create empty program files and two rather boring main programs. You
can experiment with the makefile by "touching" the source files. See
man touch.
Do you understand what is going on in the following command session?
orcas% touch lib.h queue.h queue.c lib.c
orcas% echo "void main() {}" | tee main.c > queue_test.c
orcas% make
gcc -c queue.c -o queue.o
gcc -c lib.c -o lib.o
gcc -c queue_test.c -o queue_test.o
gcc -o queue_test queue.o lib.o queue_test.o
gcc -c main.c -o main.o
gcc -o main queue.o lib.o main.o
orcas% touch queue.h
orcas% make
gcc -c queue.c -o queue.o
gcc -c queue_test.c -o queue_test.o
gcc -o queue_test queue.o lib.o queue_test.o
gcc -c main.c -o main.o
gcc -o main queue.o lib.o main.o
orcas% touch main.c
orcas% make
gcc -c main.c -o main.o
gcc -o main queue.o lib.o main.o
orcas%
See the man pages for more information. man make.