int main(int argc,char *argv[])
{
LIST_HEAD(list); //定义存放文件内容的链表
FILE *fp;

struct file_store {
char c;
struct list_head node;
} *pstore;

if(argc<2){
printf("usage: pfile <[r]>\n");
return -1;
}
if(!(fp=fopen(argv[1],"rb"))){
printf("fopen(%s) error\n",argv[1]);
return -1;
}

/* 读文件到链表 */
while(1){
if(!(pstore=(struct file_store *)malloc(sizeof(struct file_store))))
break;
pstore->c=fgetc(fp);
if(feof(fp)){
free(pstore);
break;
}
list_add_tail(&pstore->node,&list); //将本字符插入链表中
}
fclose(fp);

/* 遍历链表，输出链表中的节点个数，即文件字符数 */
int count=0;
struct list_head *p;
list_for_each(p,&list){
count++;
}
printf("%s has altogether %d character(s)\n",argv[1],count);

/* 根据命令行参数正向/反向遍历链表，输出链表中存放的字符，同时释放各节点 */
if(argc>2 && !strcasecmp(argv[2],"r")){
struct list_head *p;
list_for_each_entry_reverse(pstore,&list,node){ //反向遍历，没有保护
p=pstore->node.next;
list_del(&pstore->node);
putchar(pstore->c);
free(pstore);
/* 如果没有这一句，将报segmentation fault */
pstore=list_entry(p,struct file_store,node); //取数据项
}
}else{
struct file_store *p;
list_for_each_entry_safe(pstore,p,&list,node){ //正向遍历，有保护
list_del(&pstore->node);
putchar(pstore->c);
free(pstore);
}
}

return 0;
}