字符数组的sizeof

1、字符数组不会自动添加’\0’，字符串会自动添’\0’;

所以sizeof(c1)==3,sizeof(c4)==4;strlen(c1)==不可预知，strlen(c3)==3;

2、sizeof结果是变量所占内存大小；strlen结果是遇到的第一个’\0’之前的字符数。

#include <stdio.h>

int main(void)
{
	char c1[] = {'a', 'b', 'c'};
	char c2[] = {'a', 'b', 'c', '\0'};
	char c3[10] = {'a', 'b', '\0', 'c'};
	char c4[] = "abc";

	printf("%d\n", sizeof(c1));
	printf("%d\n", sizeof(c2));
	printf("%d\n", sizeof(c3));
	printf("%d\n", sizeof(c4));

	printf("%d\n", strlen(c1));
	printf("%d\n", strlen(c2));
	printf("%d\n", strlen(c3));
	printf("%d\n", strlen(c4));

	return 0;
}

 

输出：

3
4
10
4
5
3
2
3