popen/pclose introduce

int main(int argc, char *argv[])
{
       char buf[128];
         FILE *pp;

         if( (pp = popen("ls -al", "r")) == NULL )
         {
                 printf("popen() error!\n");
                 exit(1);
         }

         while(fgets(buf, sizeof buf, pp))
         {

                 printf("%s", buf);
         }
         pclose(pp);
         return 0;
}