C基础--字符串操作函数（strlen，strcpy,strcmp,strcat,strstr，strtok,strchr）

#include <stdio.h>
#include <string.h>
int main(void)
{
    //char dest[10];
    //#define NULL (void *)0
    //char *dest = NULL;            //dest是野指针，指向的区域没有可读写空间
    //char dest[3];
    
    //char src[] = "hello";
    char str1[10] = "hello";
    //char str2[10] = str1;
    strcpy(str2, str1);
    printf("%s\n", str2);

    //printf("%s\n", strcpy(dest, src));
    //printf("%s\n", strncpy(dest, src, sizeof(dest)));

    return 0;
}

#include <stdio.h>
#include <string.h>
hello
helloworld
strncmp("hello", "helloworld", 5);
int main(void)
{
    int i;
    char name[][10] = {"xiaoming", "itcast", "xiaoqiang", "xiaohong"};
    char key[10];
    /*
    char a[10] = "xiaoming";    //name[0]  == > a
    char b[10] = "itcast";
    char c[10] = "xiaoqiang";
    char d[10] = "xiaohong";
    */
    //char name[][10] = {"xiaoming\0\0itcast\0\0\0\0xiaoqiang\0xiaohong\0\0"};

    for (i = 0; i < 4; i++) 
    {
        if (strcmp(name[i], "xiaohong") == 0) {
            printf("%d\t%s\n", i, name[i]);
            strcpy(key, name[i]);
        }
    }
    printf("%s\n", key);
    
    return 0;
}

#include <stdio.h>
#include <string.h>
int main(void)
{
    //char s1[10] = "hello";    
    //char *s1 = "hello";    
    char s1[7] = "hello";   //注意S1要有足够的空间放拼接后的字符串，不然发生数组越界 
    char s2[] = "BOY";

    strcat(s1, s2);

    printf("%s\n", s1);
    
    return 0;
}

#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
    char str[] = "hello world itcast";
    char key;
    printf("%s\n", str);
    key = getchar();
    char *p = NULL;
    p = strchr(str, key);

    (!p)?printf("un find\n"):printf("%s\n", p);

    return 0;
}

 

#include <stdio.h>
#include <string.h>
/*
int main(void)
{
    char str[] = "hello world itcast good";
    char *p;

    p = strtok(str, " ");
    printf("%s\n", p);
    while ((p = strtok(NULL, " ")) != NULL)
        printf("%s\n", p);
//    p = strtok(str, " ");

    //printf("str = %s\n", str);

    return 0;
}
*/
/*
int main(void)
{
    char str[] = "hello, world, itcast! good.; night?";
    char *dlim = " ,?!.;";
    //char dlim[] = ".?!.;";
    char *p;

    p = strtok(str, dlim);
    printf("%s\n", p);
    while ((p = strtok(NULL, dlim)) != NULL)
        printf("%s\n", p);
//    p = strtok(str, " ");

    //printf("str = %s\n", str);

    return 0;
}
*/
size_t strlen(const char *str)
{
    return 6;
}
int main(void)
{
    char str[] = "hello world itcast good night";
    char tmp[] = "I am a student\n";
    char *dlim = " ";
    char *p;
    printf("%d\n", (int)strlen(tmp));

    p = strtok(str, dlim);  //内部指针保存下一次要strtok的字符串地址
    printf("%s\n", p);

    p = strtok(tmp, dlim);
    printf("%s\n", p);

    while ((p = strtok(NULL, dlim)) != NULL)
        printf("%s\n", p);

    return 0;
}

 

#include <stdio.h>

int a = 3;
int b;

int main(void)
{
    int c = 3;
    char *str1 = "hello";     //"hello"属于字符串常量，存储在只读数据区
    char str2[]  = "hello";  //str2[6] 内存的栈上分配,栈的属性可读可写
    printf("%p\n", &a);
    printf("%p\n", &b);
    printf("%p\n", &c);
    printf("%p\n", str1);
    printf("%p\n", &str1);
    printf("%p\n", str2);  //str2+1
    printf("%p\n", &str2);// &str2+1

    return 0;
}