mystr函数 mystrcpy mystrncmp mystrtok mystrlen

左手的ㄟ右手 2022-09-20 15:22 19阅读 0赞

//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