Recently, my little brother is always wanting to mess around and doesn’t want to study hard. This won’t work. I have to find a way and put in some effort, so I wrote a check-in program for myself;
This program is based on the Sqlite database and implements a simple check-in function. This function has the function of automatic initialization. When it is used for the first time, it will automatically create the database and table and assign the original initial value; after entering the interface, it will automatically display the last check-in date and The number of days has been clocked in; the user can choose to open or not to log out according to the prompts;
firstly, the effect picture is as follows:
This program is actually a very basic version, with only a simple clock-in record function, so it is also very suitable for beginners who have just learned sqlite. practise;
If you are more proficient, you can enrich various functions based on this program and make a variety of more interesting systems, such as: access to face recognition to make an attendance check-in system; Just email you crazily; or convert it into a dictionary, as long as you have rich imagination, you can do a lot;
Well, before looking at the code formally, let’s briefly understand a few basic functions of sqlite:
sqlite3_open(const char *filename, sqlite3 **ppDb)
打开一个指向 SQLite 数据库文件的连接，返回一个用于其他 SQLite 程序的数据库连接对象。
如果打开时没有该filename的数据库，则会自动创建改名字的数据库
sqlite3_close(sqlite3*)
该例程关闭之前调用 sqlite3_open() 打开的数据库连接。所有与连接相关的语句都应在连接关闭之前完成。
如果还有查询没有完成，sqlite3_close() 将返回 SQLITE_BUSY 禁止关闭的错误消息。
const char *sqlite3_errmsg(sqlite3*);
返回sqlite执行错误的错误信息
sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void *data, char **errmsg)
提供了一个执行 SQL 命令的快捷方式，SQL 命令由 sql 参数提供，可以由多个 SQL 命令组成。
简单来说就是通过该函数来执行sql语句
在这里，第一个参数 sqlite3 是打开的数据库对象，sqlite_callback 是一个回调，
data 作为其第一个参数，errmsg 将被返回用来获取程序生成的任何错误。
The callback function sqlite_callback in sqlite3_exec has a fixed format, as follows:
int callback(void *arg, int column_size, char *column_value[], char *column_name[])
Among them:
void *arg: the fourth parameter of the sqlite3_exec function
column_size: the number of fields in the database
column_value[]: the value of
the column column_name: the name of the field
After understanding the above functions, take a look at the system code, which has been commented in detail;
#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sqlite3.h>
#include <time.h>
#define BUFSIZE 32
char sql[128];
//用于存放打卡天数和打卡时间
struct Data
{
int day;
char date[BUFSIZE];
};
sqlite3 *db;
char dbName[32] = "info.db"; //默认创建的数据库名叫info.db
/*用来判断info.db数据库是否存在，如果不存在则在初始化时创建数据库和表*/
int isExist(void *arg, int column_size, char *column_value[], char *column_name[])
{
if (*column_value[0] == '0')
{
*(int*)arg = 0; //即将existFlag置为0，表示不存在info表格,需要创建
}
return 0;
}
/*初始化数据库：如果已经存在info.db和info表格则不操作，如果不存在，则自动创建数据库和表，并赋初值*/
int db_init()
{
int ret;
int existFlag = 1; //先默认数据库info.db是存在的
char *errMesg = NULL;
if ((ret = sqlite3_open(dbName,&db)) == SQLITE_OK)
{
printf("open %s success\n",dbName);
}else{
printf("error:%s,%d\n",sqlite3_errmsg(db),ret);
return -1;
}
//查询表格是否存在
strcpy(sql,"SELECT count(*) FROM sqlite_master WHERE type='table' AND name = 'info'");
ret = sqlite3_exec(db,sql,isExist,&existFlag,&errMesg);
if (ret != SQLITE_OK)
{
fprintf(stderr,"SQL error:%s\n",errMesg);
sqlite3_free(errMesg); //释放掉内存空间
}
if (existFlag == 0 )
{
//创建表
strcpy(sql,"create table info(day integer,date char);");
ret = sqlite3_exec(db,sql,NULL,NULL,&errMesg);
if (ret != SQLITE_OK)
{
fprintf(stderr,"SQL error:%s\n",errMesg);
sqlite3_free(errMesg);
}
//往表中插入原始数据
strcpy(sql,"insert into info values(0,'20200101');");
ret = sqlite3_exec(db,sql,NULL,NULL,&errMesg);
if (ret != SQLITE_OK)
{
fprintf(stderr,"SQL error:%s\n",errMesg);
sqlite3_free(errMesg);
}
}
sqlite3_free(errMesg);
}
/*用来从数据库中捞取数据*/
int get_data(void *arg, int column_size, char *column_value[], char *column_name[])
{
int i;
struct Data *dataInfoTmp;
dataInfoTmp = (struct Data *)arg; //将void型强制转化为 struct Data*型
strcpy(dataInfoTmp->date,column_value[1]); //将数据库存放的第二列的值，即日期赋给dataInfoTmp->date
dataInfoTmp->day = atoi(column_value[0]); //将打开天数赋给dataInfoTmp->day，atoi() :Convert char into int
return 0;
}
/*用户确认打卡后，刷新数据库数据*/
int sign_in(struct Data *arg)
{
struct Data *infoDataTmp = NULL;
infoDataTmp = arg;
char *errMesg = NULL;
int ret;
//日期相关
time_t timep;
struct tm* tm;
time(&timep);
tm = localtime(&timep);
strftime(infoDataTmp->date,BUFSIZE,"%Y-%m-%d %H:%M",tm); //将日期字符串制作成自己想要的格式
//update the day
infoDataTmp->day += 1;
//刷新数据库数据
memset(sql,0,sizeof(sql));
sprintf(sql,"update info set day=%d,date='%s';",infoDataTmp->day,infoDataTmp->date);
ret = sqlite3_exec(db,sql,get_data,&infoDataTmp,&errMesg);
if (ret != SQLITE_OK)
{
fprintf(stderr,"SQL error:%s\n",errMesg);
sqlite3_free(errMesg);
}
return 0;
}
int main()
{
int ret,len;
char cmd[BUFSIZE] = {
'\0'}; //存放用户输入的指令
char *errMesg = NULL;
struct Data infoData;
db_init(); //初始化数据库
//捞取数据库数据到结构体infoData中
strcpy(sql,"select * from info;");
ret = sqlite3_exec(db,sql,get_data,&infoData,&errMesg);
if (ret != SQLITE_OK)
{
fprintf(stderr,"SQL error:%s\n",errMesg);
sqlite3_free(errMesg);
}
//初始化界面
printf("========欢迎来打卡========\n");
printf("上次打卡是：%s,已打卡%d天\n",infoData.date,infoData.day);
while(1)
{
memset(cmd,'\0',sizeof(cmd));
printf("确认打卡请输入Y，退出输入Q:\n");
scanf("%s",cmd);
getchar();
if(strcmp(cmd,"Y") == 0)
{
sign_in(&infoData);
printf("已打卡\n");
break;
}
else if (strcmp(cmd,"Q") == 0)
{
sqlite3_free(errMesg);
printf("退出打卡\n");
break;
}
else
{
printf("输入错误，请重新输入:\n");
}
}
return 0;
}
In fact, the while(1) process in this program can be considered to open one more thread or encapsulate it into a function, so that the code will be more concise, and the little brother here is too lazy to change it, and everyone can modify it by themselves; it is purely for fun, so If there are bad things written, everyone is welcome to correct and criticize;