my_strcpy.c

《LINUX C编程实战》（作者：童永清

#include <stdio.h>
#include <string.h>

char *my_strcpy(char *strDest, const char *strSrc)
{
	char	*p_return = strDest;
	
	// 检查参数指针是否为空
	if (strDest == NULL || strSrc == NULL) {  
		fprintf(stderr, "NULL POINT!");
		return NULL;
	}
	
	while ( (*strDest++ = *strSrc++) != '\0')
		;
	return p_return;
}

int main()
{
	char	string1[32];
	char	string2[32];
	int	c;
	int	i = 0;

	printf("please input your string:");
	// 对输入字符串的长度进行检查
	while (  ( (c = getchar()) != '\n' ) && (c != EOF) && (i < 31)  )  {
		string2[i] = c;
		i++;
	}
	string2[i] = '\0';

	// 对返回值也进行合法性检查
	if (my_strcpy(string1, string2) == NULL) {
		fprintf(stderr, "return from my_strcpy");
		exit(1);
	}

	printf("string1:%s\n", string1);
	printf("string2:%s\n", string2);

	return 0;
}