我正在研究一个问题,我fork()在C语言调用之前和之后检查值和地址.我的方法是显示变量值和地址,假设看到后面的地址有差异fork().令我惊讶的是,所说的变量仍然是相同的.
我的问题是他们为什么一样？如果我改变孩子的变量会怎么样？父母和孩子都会改变吗？如果没有,我如何能够更改该地址中的值,而父地址和子地址的地址相同.
代码(供参考):
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
int main()
{
int status;
pid_t pid;
int a = 123456;
float b = 123.456;
char c = 'Z';
int *e;
e=&a;
//Retriving address's
void *ap=&a, *bp=&b, *cp=&c, *ep=&e;
printf("Parent Before Fork:\n");
printf("Integer a: \tvalue = %d, \taddress = %p\n", a, ap);
printf("Float b: \tvalue = %f, \taddress = %p\n", b, bp);
printf("Char c: \tvalue = %c, \t\taddress = %p\n", c, cp);
printf("Pointer e: \tvalue …所以我有这段代码:
String username = props.getProperty("jdbc.username");
try {
String username = parts[1];
// Check procedure
System.out.println("Checking user");
// Check database user table for username
conn = getSQLConnection();
Statement stat = conn.createStatement();
ResultSet user = stat.executeQuery( "SELECT * FROM USER WHERE log_id='" + username + "';" );
// Check given password against user entry
if(user.next()){
System.out.println("User Exists: " + username);
sendMessage("true");
return;
}
else{
System.out.println("User Does Not Exist: " + username);
sendMessage("false user");
return;
}
出于教育目的,即使我知道输入来自哪里,SQL语句是否受SQL注入保护？
我有一个按钮,我想在点击它时调用一个函数.现在它只是测试.就在我现在运行它时,按钮似乎无法点击开始.
index.html的:
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="UTF-8">
<link rel="stylesheet" type="text/css" href="css/stylesheet.css"/>
<script type="text/javascript" src="javascript/javascript.js"></script>
</head>
<body>
<h1>
<img src="#" alt=""/>
</h1>
<h3>1. Getting Store categories</h3>
<button onclick="getCategories()">Click here to Get Categories.</button>
<p></p>
</body>
</html>
javascript.js:
function getcategories()
{
alert("TEST");
}
EDDIT:stylesheet.css:
* {
font-family: Ariel, Verdana, sans-serif;
}
h1 {
text-align: center;
color: #fff;
text-shadow: 0px 1px 0px #999, 0px 2px 0px #888, 0px 3px 0px #777, 0px 4px 0px #666, 0px 5px 0px #555, 0px 6px 0px …