Shared Libraries - Hello World

#ifndef LIBHELLO_H
#define LIBHELLO_H

void say_hello();

#endif  // LIBHELLO_H

#include <stdio.h>

void say_hello() {
    puts("Hello, I am a shared library");
}

#include <stdio.h>
#include "libhello.h"

int main() {
    say_hello();
    return 0;
}

CC = gcc
CFLAGS = -Wall -Werror
TARGETS = test1 test2 test3

all: $(TARGETS)

lib: libhello.c
	$(CC) -c $(CFLAGS) -fpic $<
	$(CC) -shared -o libhello.so libhello.o

test1: test.c lib
	$(CC) -L. $(CFLAGS) -o $@ $< -lhello

test2: test.c lib
	$(CC) -L. -Wl,-rpath=. $(CFLAGS) -o $@ $< -lhello

test3: test.c lib install
	$(CC) $(CFLAGS) -o $@ $< -lhello
	@#ldd test_libhello3 | grep hello

install:
	sudo install -m755 ./libhello.so /usr/lib
	sudo ldconfig
	@#ldconfig -p | grep hello

uninstall:
	sudo rm -f /usr/lib/libhello.so
	sudo ldconfig

clean: uninstall
	rm -f *.o *.so $(TARGETS)

#!/bin/sh

test1() {
    echo test1: LD_LIBRARY_PATH
    make -s test1
    export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
    ./test1
    unset LD_LIBRARY_PATH
    make -s clean
}

test2() {
    echo test2: rpath
    make -s test2
    ./test2
    make -s clean
}

test3() {
    make -s test3
    echo test3: ld.so
    ./test3
    make -s clean
}

test1
echo
test2
echo
test3