use apache apr ,but compile error

[liangwu2046]

The below is my program:


/////////////////////////////////////////
//hello.c
#include <apr_pools.h>
#include <apr_general.h>
int main(void)
{
apr_pool_t *p;
apr_initialize();
return 1;
}
/////////////////////////////////////////
gcc -I usr/local/apache2/include/ -L usr/local/apache2/lib/ hello.c -o hello
........
undefined reference apr_initialize()


As you see,the program is easy,but when I compile it ,it has a error,I don't why, who can tell me the reason?