20、树莓派编程：从C到C++及面向对象编程基础

树莓派编程：从C到C++及面向对象编程基础

1. C语言字符串操作与LED控制

在C语言编程中，字符串操作是基础且重要的部分。以下是一个字符串操作的示例代码：

// find and replace the w with a W
char *p = strchr(c,'w');  // returns pointer to first 'w' char
*p = 'W';
printf("The string c is now: %s\n", c);
if (strcmp("cat", "dog")<=0){      // ==0 would be equal
    printf("cat comes before dog (lexiographically)\n");
}
//insert "to the" into middle of "Hello World!" string - very messy!
char *d = " to the";
char *cd = malloc(strlen(c) + strlen(d));
memcpy(cd, c, 5);
memcpy(cd+5, d, strlen(d));
memcpy(cd+5+strlen(d), c+5, 6);
printf("The cd string is: %s\n", cd);
//tokenize cd string using spaces
p = strtok(cd," ");
while(p!=NULL){
    printf("Token:%s\n", p);
    p = strtok(NULL, " ");
}
return 0;