网络编程模拟面试题总结， sqlite3的c语言调用，

1 数据库的插入删除改变和查看

int do_insert(sqlite3* db);
int do_delet(sqlite3* db);
int do_select(sqlite3*db);
int do_change(sqlite3* db);
/*sqlite3* db=NULL;*/
 
int main(int argc, const char *argv[])
{
	sqlite3* db=NULL;
	if(sqlite3_open("./my.db",&db)){
		printf("%s\n",sqlite3_errmsg(db));
		return -1;
	}
	printf("sqlite3_open success\n");
	char str[128]="create table if not exists stu (id int key,name char,score int)";
	char*errmsg=NULL;
	if(sqlite3_exec(db,str,NULL,NULL,&errmsg)!=SQLITE_OK){
		fprintf(stderr,"create failed __%d__\n",__LINE__);
		return -1;
	}
	char c=0;
	while(1){
		system("clear");
		printf("------------------\n");
		printf("------------------\n");
		printf("------1.insert----\n");
		printf("------2.delet-----\n");
		printf("------3.change----\n");
		printf("------4.select----\n");
		printf("------5.quit------\n");
		printf("------------------\n");
		c=getchar();
		while(getchar()!='\n');
		switch (c){
		case'1':
			do_insert(db);
			break;
		case'2':
			do_delet(db);
			break;
		case'3':
			do_change(db);
			break;
		case'4':
			do_select(db);
			break;
		case'5':
			goto END;
		}
		fprintf(stderr,"input space clear>>");
		while(getchar()!='\n');
	}
END:
		sqlite3_close(db);
		return 0;
}
int do_insert(sqlite3* db){
	int id=0;
	char name[20]="";
	int score=0;
	printf("please input id>>");
	scanf("%d",&id);
	while(getchar()!='\n');
 
	printf("please input name>>");
	scanf("%s",name);
	while(getchar()!='\n');
 
	printf("please input score>>");
	scanf("%d",&score);
	while(getchar()!='\n');
 
	char str[128]="";
	sprintf(str,"INSERT INTO stu values(%d, \"%s\",%d);",id,name,score);
 
	char*errmsg=NULL;
	if(sqlite3_exec(db,str,NULL,NULL,&errmsg)!=SQLITE_OK){
		fprintf(stderr,"insert failed __%d__\n",__LINE__);
		return -1;
	}
	fprintf(stderr,"insert in to stu success\n");
	printf("id=%d,name=%s,score=%d\n",id,name,score);
	return 0;
}
int do_delet(sqlite3* db){
	do_select(db);
	int id=0;
	printf("please input the id who needing be deleted>>");
	scanf("%d",&id);
	while(getchar()!='\n');
 
 
	char str[128]="";
	sprintf(str,"delet from stu where id=%d;",id);
 
	char*errmsg=NULL;
	if(sqlite3_exec(db,str,NULL,NULL,&errmsg)!=SQLITE_OK){
		fprintf(stderr,"deletion be failed __%d__\n",__LINE__);
		return -1;
	}
	fprintf(stderr,"delet id=%d from stu success\n",id);
	return 0;
}
int do_change(sqlite3* db){
again:
	do_select(db);
	int id=0;
	char name[20]="";
	int score=0;
	printf("please input the id who needing be changed>>");
	scanf("%d",&id);
	while(getchar()!='\n');
	printf("please input the member from stu who need change:");
	printf("1.name 2.score\n");
	char ctrl=getchar();
	if('1'==ctrl){
		printf("please input the new name:");
		scanf("%s",name);
		char str[128]="";
		sprintf(str,"update stu set name=%s where id=%d;",name,id);
 
		char*errmsg=NULL;
		if(sqlite3_exec(db,str,NULL,NULL,&errmsg)!=SQLITE_OK){
			fprintf(stderr,"deletion be failed __%d__\n",__LINE__);
			return -1;
		}
		fprintf(stderr,"delet id=%d from stu success\n",id);
	}else if('2'==ctrl){
		printf("please input the new score:");
		scanf("%d",&score);
		char str[128]="";
		sprintf(str,"update stu set score=%d where id=%d;",score,id);
 
		char*errmsg=NULL;
		if(sqlite3_exec(db,str,NULL,NULL,&errmsg)!=SQLITE_OK){
			fprintf(stderr,"deletion be failed __%d__\n",__LINE__);
			return -1;
		}
		fprintf(stderr,"delet id=%d from stu success\n",id);
 
	}else{
		printf("input error!\n");
		printf("please input again");
		while(getchar()!='\n');
		goto again;
	}
	printf("change success\n");
	return 0;
}
int do_select(sqlite3*db){
	char str[128]={0};
	sprintf(str,"select * from stu;");
	char* errmsg=NULL;
	char**retPtr=NULL;
	int row;
	int column;
	if(sqlite3_get_table(db,str,&retPtr,&row,&column,&errmsg)!=SQLITE_OK){
		fprintf(stderr,"get_table failed __%d__,errno=%s\n",__LINE__,errmsg);
		return -1;
	}
	for(int i=0;i<row;i++){
		for(int j=0;j<column;j++){
			fprintf(stderr,"%-8s\t",*(retPtr+(i*column)+j));
		}
		putchar(10);
	}
	printf("select success\n");
}

2 模拟面试试题

（1）IO多路复用的原理：将需要监控的文件描述符放到一个容器内统一监管，一旦容器中的文件描述符有一个或多个对应的事件产生，就会将阻塞解除，去执行接下来的代码。

（2）select和poll的区别：select是将fdset拷贝到内核，通过循环遍历每个fd文件描述符来监控事件，所以上述缺陷倒置select最多只能监控1024个文件描述符，而poll没有这个限制。

（3）数据库sqlite3函数有哪些：sqlite3_open sqlite3_close sqlite3_exec sqlite3_get_table

sqlite3_free_table

sqlite3_exec的第三个参数是一个回调函数，每当exec所执行的语句有一个结果就会调用一次该回调函数。

（4）什么是IO：一个程序与外部设备间的信息交互

（5）文件IO的函数谁提供？标准IO的函数谁提供？：系统内核提供，c语言库提供

（6）消息队列和共享内存的区别：消息队列内的信息在被读取之前一直存在，不易丢失，共享内存只要有一方改变其中内容，其内容就会被实时更新，实时性好

（7）野指针产生情况：未初始化的指针，释放后未指向NULL的指针，访问数组越界的指针，指向非法内容的指针。