正点原子Linux C 应用编程 点亮LED学习代码（基于IMX6ULL开发板），教程使用的是系统调用，我使用的是标准I/O

#include "stdio.h"      //标准I/O库和printf函数需使用
#include "string.h"     //strcmp函数需使用char tigger_file_addr[] = "/sys/class/leds/sys-led/trigger";
char brightness_file_addr[] = "/sys/class/leds/sys-led/brightness";FILE *file1 = NULL;
FILE *file2 = NULL; 
int ret = 0;/*
*需要给main函数传参时的写法
*argc：参数数量
*argv[]:参数储存数组
*/
int main(int argc, char *argv[])
{__uint8_t i = 0;printf("    传入参数个数=%d\n",argc);for(i=0; i<argc; i++){printf("    参数%d的内容为:%s\n",i,argv[i]);}/*以可读可写方式打开文件 trigger */       file1 = fopen(tigger_file_addr, "r+");if (file1 == NULL)//文件打开失败{perror("    fopen tigger_file");return 1;}printf("    tigger_file open success\n");/*以可读可写方式打开文件 brightness */  file2 = fopen(brightness_file_addr, "r+");if (file2 == NULL)//文件打开失败{perror("    fopen brightness_file");return 1;}printf("    brightness_file open success\n");if (argc == 2){if( (strcmp("on",argv[1]) == 0) ||  (strcmp("off",argv[1]) == 0))//如果传入参数为on/off{printf("    执行%s操作\n",argv[1]);ret = fwrite("none", 1, 4, file1);//将触发方式改为noneif(ret != 4){if(ferror(file1) != 0) printf("    write none to tigger_file error!\n");return 1;}else printf("    write none to tigger_file success!\n");fclose(file1);//关闭trigger文件if( strcmp("on",argv[1]) == 0)//如果传入参数为on{ret = fwrite("1", 1, 1 ,file2);//要写入的字符串、每个数据项的大小，数据项的数量 if(ret != 1){if(ferror(file2) != 0)printf("    write 1 to brightness_file error!\n");return 1;}elseprintf("    write 1 to brightness_file success!\n");  }else{ret = fwrite("0", 1, 1 ,file2);//要写入的字符串、每个数据项的大小，数据项的数量 if(ret != 1){if(ferror(file2) != 0)printf("    write 0 to brightness_file error!\n");return 1;}elseprintf("    write 0 to brightness_file success!\n");  }           fclose(file2);//关闭brightness文件}   else if( strcmp("heartbeat",argv[1]) == 0)//如果传入参数为on{printf("    执行%s操作\n",argv[1]);ret = fwrite("heartbeat", 1, 9, file1);//将触发方式改为noneif(ret != 9){if(ferror(file1) != 0)printf("    write heartbeat to brightness_file error!\n");return 1;}elseprintf("    write heartbeat to brightness_file success!\n");  fclose(file1);//关闭trigger文件fclose(file2);//关闭brightness文件}    }return 0;
}