简单Demo

void diamond(int r){        int x,y;    for ( y = 0; y<=2*r; y++) {        for (x = 0; x<=2*r; x++) {            if (y <= x+r&& y >=x-r && y >=-x+r && y<=-x+3*r) {                printf("*");            }            else{                printf(" ");            }        }        printf("\n");    }}void MMapDemo(){        int *p = mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, 0, 0);        *p = 20;    *(p+1) = 30;    *(p+2) = 40;        printf("%d\n",p[2]);    munmap(p, 4096);    printf("%d\n",getpagesize());}