# 改變字符串的值 ## 例子 #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調試程序時，可以用“`set`”命令改變字符串的值，以上面程序為例： (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; 可以看到執行`p1`和`p2`的字符串都發生了變化。也可以通過訪問內存地址的方法改變字符串的值： 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; 在改變字符串的值時候，一定要注意內存越界的問題。 參見[stackoverflow](http://stackoverflow.com/questions/19503057/in-gdb-how-can-i-write-a-string-to-memory). ## 貢獻者 nanxiao