UNIX for Advanced & Expert Users

// shared.c
// compile like:  gcc shared.c -shared -fPIC -o shared.so
#include <stdio.h>

int library_function(int argc, char *argv[])
{
        fprintf(stderr, "library_function called\n");
        return(0);
}

// main.c
// compile like:  gcc main.c -ldl -o main
#include <stdio.h>
#include <dlfcn.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main(int argc, char *argv[])
{
        void *h=dlopen("./shared.so", RTLD_NOW);
        int (*fn)(int argc, char *argv[]);
        pid_t pid;

        if(h == NULL)
        {
                fprintf(stderr, "Couldn't open shared.so\n");
                return(1);
        }

        fn=dlsym(h, "library_function");
        if(fn == NULL)
        {
                fprintf(stderr, "Couldn't find library_function\n");
        }

        pid=fork();  // Create new process
        if(pid == 0)    // child code
        {       return(fn(argc, argv));         }
        else // Wait for child process
        {
                int status;
                wait(&status);
                fprintf(stderr, "Child returned %d\n", WEXITSTATUS(status));
        }

        dlclose(h);

        return(0);
}