什么是\\ 0符号在C字符串是什么意思？ [英] What does the \0 symbol mean in a C string?

问题描述

考虑以下code：

char str[]= "Hello\0";

这是海峡阵列的长度，并与它多少0结束？

What is the length of str array, and with how much 0s it is ending?

推荐答案

sizeof的STR 为7 - 五个字节为你好的文字，再加上明确的NUL终止，加上隐含的NUL终止符。

sizeof str is 7 - five bytes for the "Hello" text, plus the explicit NUL terminator, plus the implicit NUL terminator.

的strlen（STR）是5 - 五你好只字节

strlen(str) is 5 - the five "Hello" bytes only.

这里的关键是，隐含的NUL终止符是的总是的补充 - 即使字符串正好与结束\\ 0 。当然，的strlen 只是停止在第一个 \\ 0 - 它不能分辨

The key here is that the implicit nul terminator is always added - even if the string literal just happens to end with \0. Of course, strlen just stops at the first \0 - it can't tell the difference.

有一个例外的隐含NUL终止规则 - 如果明确指定数组大小，字符串将被截断以适应：

There is one exception to the implicit NUL terminator rule - if you explicitly specify the array size, the string will be truncated to fit:

char str[6] = "Hello\0"; // strlen(str) = 5, sizeof(str) = 6 (with one NUL)
char str[7] = "Hello\0"; // strlen(str) = 5, sizeof(str) = 7 (with two NULs)
char str[8] = "Hello\0"; // strlen(str) = 5, sizeof(str) = 8 (with three NULs per C99 6.7.8.21)

这是，然而，很少有用，而且容易错估字符串的长度，并用未终止的字符串结束了。它也禁止在C ++中。

This is, however, rarely useful, and prone to miscalculating the string length and ending up with an unterminated string. It is also forbidden in C++.

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