c语言字符串基本方法

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

//c语言惯例：#define中的标识符都是大写
#define PI 3.1415f    //在预编译的时候会把PI替换成一个字符序列
const float a = 10.8f;
struct {
	int age;
	int height;
	char name[40];
} my_first_horse = { 10, 50, "horse" };

int main() {
	puts("c语言!!!Hello World!!!"); /* prints !!!Hello World!!! */
	printf("%.2f\n", PI); // 输出一个folat数值
	//对字符串的操作

	char str2[5];
	str2[0] = 'a';
	str2[1] = 'a';
	str2[2] = 'a';
	str2[3] = 'a';
	str2[4] = '\0'; //\0是字符串的结尾标识符,ascII值为0

	//	printf("str:%s\n", str);
	printf("str2[4]:%i\n", str2[3]);
	printf("str2:%s\n", str2);

	char str[20];//= "this is a c string "; //才语言中使用char来代替string
	char say[] = "this is your name";
	printf("int length: %d\n", sizeof(int));
	//字符串总是以\0结尾的,所以字符串的长度永远比字符串中的字符数多1
//	size_t n = 10;
//	printf("%s\n", strcpy(str, say)); //把s2中的内容复制到s1中 复制一个字符串,遇到"\0"后停止
//	printf("%s\n", strncpy(str, say, n)); //把s2中的内容复制到s1中
//	memcpy(str, say, 3);
	printf("haha:%s\n", (char *) memcpy(str, say, 8));
str[6] = '\0';
	printf("%s\n", str); //把s2中的内容复制到s1中
	printf("%s\n", strncat(str, say, 10)); //连接字符串
	strcpy(str, say);
	strncpy(str, say, 3);
	strcat(str, say);
	strncat(str, say, 3);

	char s1[] = "hello";
	char s2[] = "liupeng";
	char s3[] = "hello";
	printf("%i\n", memcmp(s1, s2, 3));
	printf("%i\n", strcmp(s1, s3));
	printf("%i\n", strncmp(s2, s1, 3));

	char *pc = strchr(s1, 'l'); //返回在s1中第一次出现l的位置指针
	pc = strrchr(s1, 'l'); //返回在s1中最后一次出现l的位置指针
	pc = strstr(s1, "el"); //返回在s1中第一次出现字符串el的位置指针
	printf("%s\n", pc);

	printf("%d", strlen(s1));  //计算实际的长度,不包含\0

	//	printf("program name:%s\n", argv[0]);
	////	for (int i = 1; i < argc; i++) {
	//		printf("program arg:%s\n", argv[1]);
	//	}

	//	printf("%i", my_first_horse.age);
	return 0;
}