mydlopen-sample.c

#include <stdio.h>
#include <dlfcn.h>
#include <sys/types.h>

int main(void) {
  void *handle = dlopen("/usr/lib/libc.dylib", RTLD_LAZY);
  unsigned int (*mysleep)(unsigned int) = dlsym(handle, "sleep");
  int (*myfork)(void) = dlsym(handle, "fork");
  void (*mywait)(int*) = dlsym(handle, "wait");
  pid_t (*mygetpid)(void) = dlsym(handle, "getpid");
  int pid = myfork();
  if (pid == 0) {
    printf("[%d] yay!\n", mygetpid());
    mysleep(1);
    printf("[%d] yay!\n", mygetpid());
    return 0;
  }
  printf("[%d] pid:%d\n", mygetpid(), pid);
  printf("[%d] wait...\n", mygetpid());

  int status;
  mywait(&status);
  printf("[%d] done! status:%d\n", mygetpid(), status);

  dlclose(handle);
  return 0;
}