CString子串问题

Question

我在使用文件 i/o 实现的子字符串方面遇到问题。我有 char data[21]、char world[21] 和 char eat[21]，它们将是 char in[300] 的子字符串（顺便说一句，这些名称没有任何意义）。我想出了一些子字符串代码，但我没有得到我想要的子字符串，而是得到了整个字符串和一些时髦的字符。有人可以告诉我我做错了什么，或者如果我只是在过去的几个小时内省去了时间并且库中已经有一个子 Cstring 方法？

int main()
{
    char in[300] = "w54;d68;n541;"  // this is bigger than it needs to be because its for file i/o
    char world[21], data[21], eat[21];
    int w, d, n, end1, end2, end3;

    for (w = 0; in[w] != 'w'; w++) {
    }

    for (end1 = w; in[end1] != ';'; end1++) {
    }

    d = end1 + 1;

    for (end2 = d; in[end2] != ';'; end2++) {
    }

    n = end2 + 1;

    for (end3 = n; in[end3] != ';'; end3++) {
    }

    int i;

    for (i = w + 1; i < end1; i++) {
      append(world, in[i]);
    }

    for (i = d + 1; i < end2; i++) {
      append(data, in[i]);
    }

    for (i = n + 1; i < end3; i++) {
      append(eat, in[i]);
    }

    cout << "world[21]: " << world << endl << "data[21]: " << data << endl << "eat[21]: " << eat << endl;
}

void append(char *s, char c)
{
    int len = strlen(s);
    s[len] = c;
    s[len + 1] = '\0';
}

这是我的断点（就在 return 0 之前）结果

in  0x0021fbb8 "w54;d68;n541;5468541"   char [300]
end2    7   int
world   0x0021fb98 "ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌw54;d68;n541;5468541"   char [21]
data    0x0021fb78 "ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌw54;d68;n541;5468541"   char [21]
eat 0x0021fb58 "ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌw54;d68;n541;5468541"   char [21]

n   8   int
i   12  int
end3    12  int
w   0   int
end1    3   int

Answer 1

将 char world[21], data[21], eat[21]; 更改为

char world[21] = {0};
char data[21] = {0};
char eat[21] = {0};

char world[21] 的 strlen 如果未初始化则未定义`

Answer 2

好吧，你有几个标准库选项

substr(...) -> http://www.cplusplus.com/reference/string/string/substr/

或

strstr(...) -> http://www.cplusplus.com/reference/clibrary/cstring/strstr/

:)