C连接postgresql Dome

#include<stdio.h>
#include<stdlib.h>
/*libpq-fe.h在/postgresql-13.1/include文件下，放到/usr/include*/
#include<libpq-fe.h>
#include<string.h>

int main(int argc, char** argv) {

    /*定义用于连接数据库的常量字符串,填自己的ip，端口，用户，数据库，密码*/
    const char *conninfo="host=localhost port=5433 user=postgres dbname=postgres password=123789..";
    
    /*与数据库服务器建立连接*/
    PGconn *conn=PQconnectdb(conninfo);
  
    /*判断数据库连接是否成功，PQstatus()方法返回链接状态的枚举，连接正常则打印CONNECTION OK*/
    if(PQstatus(conn)==CONNECTION_OK){
 
        printf("connection ok\n");  

    }
    else
    {
        fprintf(stderr,"%s",conninfo);
        PQerrorMessage(conn);
        printf("connection error");
        PQfinish(conn);
    }
/*字符串拼接*/
    char commands[100];
    char age[20];
    char command[100] = "select * from test where age = ";
    printf("please input condition,age:");
    scanf("%s",age);
    strcat(commands,command);
    strcat(commands,age);
    printf("%s\n",commands);
    PGresult *res = PQexec(conn,commands);
    //PGresult *res = PQexec(conn,"SELECT * FROM test");

    /**运行查询命令*/
    if(  PQresultStatus(res)  !=  PGRES_TUPLES_OK) {
        fprintf(stderr,"Exec Query Fauled!\n");
        PQclear(res);
        return 0;
    }
    int i;
    int t;
    int k;
    int s;
    i = PQntuples(res);
    /**取得查询的结果的记录的数量*/
    t = PQnfields(res);
    /**取得字段数量*/
    for(s=0; s<i;s++) {
        for (k = 0; k<t; k++) {
            printf("%s",PQgetvalue(res,s,k));
            printf("  ");
        }
        printf("\n");
    }
    PQfinish(conn);
    PQclear(res);
    return 0;