C连接MySQL的问题?__mysql_query_phonelist_select_telephone_res_

当前位置: 技术问答>linux和unix

C连接MySQL的问题?

来源: 互联网发布时间：2015-07-01

本文导语: 源文件: #include "sql.h" char *user_name = "root"; char *user_pass = "root"; char *databasename = "zivr"; char phonelist[20]={0}; MYSQL* result; /* * * DATABASE CONNECT * */ int db_connect(char* db_name) { mysql_init(&mysql); result = mysql_real_connec...

源文件:
#include "sql.h"

char *user_name = "root";
char *user_pass = "root";
char *databasename = "zivr";
char phonelist[20]={0};
MYSQL* result;

/*
*
* DATABASE CONNECT
*
*/
int db_connect(char* db_name)
{
mysql_init(&mysql);
result = mysql_real_connect(&mysql,"localhost",user_name,user_pass,db_name,0,NULL,0);
if(result)
return 0;
else
return -1;
}
/*
*
*  UPDATE STATE
*
*/

int update_state(char* tel,char* states)
{
   sprintf(query,"UPDATE phonelist SET state = '%s' WHERE telephone = '%s'",states,tel);
   mysql_real_query(&mysql,query,(unsigned int)strlen(query));
   res = mysql_use_result(&mysql);
   mysql_free_result(res);
}
/*
* SELECT TELEPHONE FROM TABLE
*
*/

void select_telephone()
{
   sprintf(query,"SELECT telephone,dialmonth FROM phonelist WHERE state = 'Y'");
   mysql_real_query(&mysql,query,(unsigned int)strlen(query));
   res = mysql_use_result(&mysql);
   //while(row = mysql_fetch_row(res))
   row = mysql_fetch_row(res);
   strcpy(phonelist,row[0]);
   mysql_free_result(res);

}
void close_db(void)
{
  mysql_free_result(res);
}

int main(void)
{
  db_connect("zivr");
  select_telephone();
  printf("%sn",phonelist);
}
头文件

#include
#include
#include
#include

MYSQL mysql;
MYSQL_RES *res;
MYSQL_ROW row;

char query[80];

/* --------------Function List -------------- */
int db_connect(char* db_name);
int update_state(char* tel,char* states);
void select_telephone(void);
void close_db(void);

/* -------------------------------------------*/

编译使用 gcc -o zmesql zmesql.c -L/usr/lib/mysql -lmysqlclient -lz
但是运行时出现错误:
  segmentation fault
我使用gdb 调试
其中有行为select_telephone();
请问这是什么原因?

void select_telephone()
{
   if(mysql_query(&mysql,query) != 0)
{
   return;
}
res = mysql_store_result(&mysql);

if(row = mysql_fetch_row(res))
{
   strcpy(phonelist,row[0]);
}
mysql_free_result(res);
}

第一 db_connect() 中没有判断 mysql_init() 成功否
第二在调 db_connect()后没有判断数据库打开成功否，就已经开始用了
其它的还没仔细看

.h文件中做如下修改
query[1024];
*******************
.c文件做如下修改
void select_telephone()
{
    memset(query, 0, 1024);
    sprintf(query,"SELECT telephone,dialmonth FROM phonelist WHERE state = 'Y'");

    if(mysql_query(&mysql,query) != 0)
    {
   return;
    }

    res = mysql_store_result(&mysql);

    if(row = mysql_fetch_row(res))
    {
      strcpy(phonelist,row[0]);
    }
    mysql_free_result(res);
}

int main(void)
{
if(db_connect("zivr")