mystr函数 mystrcpy mystrncmp mystrtok mystrlen

(35) 2024-04-09 16:01:01
//mystrcpy

#include <stdio.h>

char *mystrcpy(char *dest, char *src)
{
	int i;
	for(i = 0; (dest[i] = src[i]); i++){ 
			;	//当src[i] = "\0" 表达式为0,0为假,条件不成立,跳出循环
		
	}

	return dest;

}

int main(int argc, char *argv[])
{
	char dest[200];
	
	printf("mystrcpy:%s\n", mystrcpy(dest, argv[1]));

	return 0;
}

/*
akaedu@akaedu-G41MT-D3:~/lin/722_str$ ./mystrcpy hellook
mystrcpy:hellook
*/<pre name="code" class="cpp">



//*******************************************
//--------------------mystrcpy1---------------


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

char *mystrcpy(char *dest, char *src)
{
	int i = 0;

	for(; (dest[i] = src[i]); i++){
			;
	}
	return dest;


}


int main(void)
{
	char dest[100];
	char src[100];
	gets(src);
//	fgets(src, 100, stdin);

	printf("%s\n", mystrcpy(dest, src) );

	return 0;
}



/*如果用fgets()会把回车也读进去//去回车输出
	int i = strlen( mystrcpy(dest, src) );
	printf("%d\n", i);

	if(dest[i-1] == '\n')
	{
		dest[i-1] = '\0';
	}

	printf("%s\n", dest);

	return 0;
	
}
--------------------------------------
akaedu@akaedu-G41MT-D3:~/lin/722_str$ ./mystrcpy1
hellow
7
hellow
--------------------------------------
*/<pre name="code" class="cpp">







//mystrncpy

#include <stdio.h>
char *mystrncpy(char *dest, char *src, int n )
{
	int i;

	for(i = 0; ( (n > 0) && (dest[i] = src[i]) ); i++, n-- ){
		
	}

	while(n >= 0){
		dest[i++] = '\0';
		n--;
	}
	
	
	//dest[i++] = '\0';
		
	
	return dest;

}




int main(int argc, char *argv[])
{
	char str[200];
	printf("mystrncpy:%s\n", mystrncpy(str, argv[1], 5));
	return 0;
}

/*
akaedu@akaedu-G41MT-D3:~/lin/722_str$ ./mystrncpy helloaaa
mystrncpy:hello
akaedu@akaedu-G41MT-D3:~/lin/722_str$ ./mystrncpy comeonbaby
mystrncpy:comeo
*/



//*******************************************
//--------------------mystrncpy1---------------


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

char *mystrncpy(char *dest, char *src, int n)
{
	int i;

//	for( i = 0; ( (i > n) &&(dest[i] = src[i]) ); i++){
//			;
//	}
	for( i = 0; ( (n > 0) &&(dest[i] = src[i]) ); i++, n--){
			;			
	}

	while( n >= 0){
		dest[i++] = '\0';
		n--;
	
	}
	return dest;


}


int main(void)
{
	char dest[100];
	char src[100];
	gets(src);

//	fgets(src, 100, stdin);

	printf("%s\n", mystrncpy(dest, src, 5) );

	return 0;
}


/*
akaedu@akaedu-G41MT-D3:~/lin/722_str$ ./mystrncpy1
hellowor ds
hello
*/


<pre name="code" class="cpp">




/***************************************************
自己实现库函数:strtok
*/

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

char *mystrtok(char *src, char *delim)
{
	char *begin, *end;
	static char *savep = "";

	begin = src ? src : savep;
	begin = begin + strspn(begin, delim);
	if(*begin == '\0'){
		savep = "";
		return NULL;
	}

	end = begin + strcspn(begin, delim);
	if(*end != '\0'){
		*end++ = '\0';
	}
	savep = end;
	return begin;
}


int main(int argc, char *argv[])
{
	char *token, *begin;

	for(begin = argv[1]; (token = mystrtok(begin, argv[2])); begin = NULL ){
	
		printf("token:%s\n", token);
	}




	return 0;
}









//************************************
//-----------mystrlen-----------------

#include <stdio.h>

int mystrlen(char *src)
{
	int i = 0;
	for(i = 0; (src[i] != '\0') ; i++){

		printf("src[%d]:%d %c\n", i, i, src[i]);

	}

	return i;

}


int main(void)
{
	char str[1024];
	fgets(str, 1024, stdin);
//	gets(str);
	printf("%d\n", mystrlen(str));

	return 0;
}

/*----------------------
hello
src[0]:0 h
src[1]:1 e
src[2]:2 l
src[3]:3 l
src[4]:4 o
src[5]:5 

5
-----------------------*/

<pre id="best-content-1042162848" class="best-text mb-10">fgets的原型是
char* fgets(char* s, int n, FILE* fp);
参数数量比较多,有3个。而fgets相比于gets有一个显著的差别就是fgets会将行末的换行符算到读入的字符串里面。所以相同且正常(输入无错误,缓冲区够大)的情况下,fgets读入的字符串会比gets在末尾'\0'前面多一个换行符;行长度超出缓冲区大小时只读入前 n-1 个字符。因此,
gets(s);
相当于
fgets(s, sizeof(s), stdin);  
if(s[strlen(s) - 1] == '\n') s[strlen(s) - 1] = '\0';   // 去掉换行符





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