【原创】字符串处理函数使用和结果

【原创】字符串处理函数使用和结果

涉及函数如下：

           strcat strcpy strlen strcmp strlwr strupr 关键字sizeof

代码如下（字符数组）：

#include "stdafx.h"
#include <string.h>
#include <limits.h>
 

int main(int argc, char* argv[])
{
	char str1[] = "I am Geng.";
	char str2[] = "I love China!";
	char str3[CHAR_MAX] = "\0";

	//在此编译环境下CHAR_MAX = 127, CHAR_MIN = -128
	printf("CHAR_MAX = %d, CHAR_MIN = %d\n", 
			CHAR_MAX, CHAR_MIN);

	printf("%d\n",strcmp(str1,str2));

	printf("str1's length %d, str2's length %d\n",
			strlen(str1),strlen(str2)); //strlen 求得的字节数不包括\0
	printf("str1's length %d, str2's length %d\n",
			sizeof(str1),sizeof(str2)); //sizeof 求得的字节数包括\0

	strcpy(str3, str2);
	printf("%d\n",strcmp(str3,str2));
	printf("str3's length %d, str2's length %d\n\n",
			strlen(str3),strlen(str2));

	printf("++ 小写变大写 ++\n");
	printf("%s\n", strupr(str1));
	printf("%s\n", strupr(str2));

	printf("++ 大写变小写 ++\n");
	printf("%s\n", strlwr(str1));
	printf("%s\n", strlwr(str2));

	return 0;
}

/* 输出结果如下
	CHAR_MAX = 127, CHAR_MIN = -128
	-1
	str1's length 10, str2's length 13
	str1's length 11, str2's length 14
	0
	str3's length 13, str2's length 13

	  ++ 小写变大写 ++
	  I AM GENG.
	  I LOVE CHINA!
	  ++ 大写变小写 ++
	  i am geng.
	  i love china!
*/

对比代码（字符指针）：

#include "stdafx.h"
#include <string.h>
#include <limits.h>
 
int main(int argc, char* argv[])
{
	char *str1 = "I am Geng.";
	char *str2 = "I love China!";
	char str3[CHAR_MAX] = "\0";
	char *pstr3 = str3;
	
	printf("CHAR_MAX = %d, CHAR_MIN = %d\n", 
		CHAR_MAX, CHAR_MIN);
	
	printf("%d\n",strcmp(str1,str2));
	
	printf("str1's length %d, str2's length %d\n",
		strlen(str1),strlen(str2)); //strlen 求得的字节数不包括\0
	printf("str1's length %d, str2's length %d\n",
		sizeof(str1),sizeof(str2)); //sizeof 求得的字节数包括\0
	
	strcpy(str3, str2);
	printf("%d\n",strcmp(str3,str2));
	printf("str3's length %d, str2's length %d\n\n",
		strlen(str3),strlen(str2));
	printf("str3's length %d, str2's length %d\n\n",
		sizeof(str3),sizeof(str2));
	
	//下面这两个函数中的参数不能是指针str1或str2,可以是数组str3或指针pstr3
	printf("%s\n", strupr(pstr3));
	printf("%s\n", strlwr(pstr3));

	return 0;
}

/*  输出结果
	CHAR_MAX = 127, CHAR_MIN = -128
	-1
	str1's length 10, str2's length 13
	str1's length 4, str2's length 4
	0
	str3's length 13, str2's length 13

	str3's length 127, str2's length 4
  
	I LOVE CHINA!
	i love china!
*/