whoami

#include
#include<unistd.h>
#include<pwd.h>
#include<sys/types.h>
int main()
{
 uid_t id;
 struct passwd *p;
 id = geteuid();//注意不是getuid;
 p = getpwuid(id);
 if(p == NULL)
  printf("I don't know who you are!\n");
 else
  printf("%s\n",p->pw_name);
 return 0;
}