改变字符串的值

#include <stdio.h>

int main(void)
{
    char p1[] = "Sam";
    char *p2 = "Bob";

    printf("p1 is %s, p2 is %s\n", p1, p2);
    return 0;
}

技巧

使用gdb调试程序时，可以用“set”命令改变字符串的值，以上面程序为例：

(gdb) start
Temporary breakpoint 1 at 0x8050af0: file a.c, line 5.
Starting program: /data1/nan/a 
[Thread debugging using libthread_db enabled]
[New Thread 1 (LWP 1)]
[Switching to Thread 1 (LWP 1)]

Temporary breakpoint 1, main () at a.c:5
5               char p1[] = "Sam";
(gdb) n
6               char *p2 = "Bob";
(gdb) 
8               printf("p1 is %s, p2 is %s\n", p1, p2);
(gdb) set main::p1="Jil"
(gdb) set main::p2="Bill"
(gdb) n
p1 is Jil, p2 is Bill
9               return 0;

可以看到执行p1和p2的字符串都发生了变化。也可以通过访问内存地址的方法改变字符串的值：

Starting program: /data1/nan/a 
[Thread debugging using libthread_db enabled]
[New Thread 1 (LWP 1)]
[Switching to Thread 1 (LWP 1)]

Temporary breakpoint 2, main () at a.c:5
5               char p1[] = "Sam";
(gdb) n
6               char *p2 = "Bob";
(gdb) p p1
$1 = "Sam"
(gdb) p &p1
$2 = (char (*)[4]) 0x80477a4
(gdb) set {char [4]} 0x80477a4 = "Ace"
(gdb) n
8               printf("p1 is %s, p2 is %s\n", p1, p2);
(gdb) 
p1 is Ace, p2 is Bob
9               return 0;

在改变字符串的值时候，一定要注意内存越界的问题。
参见 stackoverflow.