目录

1、查看mount挂载情况2、挂载虚拟文件系统3、 文件从哪里来4、内核的 sys_open、sys_read 会做什么？5、app调用系统接口图6、字符设备节点介绍7、文件拷贝实例

1、查看mount挂载情况

```go cat /proc/mounts

2、挂载虚拟文件系统

mount -t sysfs none /mnt

3、 文件从哪里来

4、内核的 sys_open、sys_read 会做什么？

5、app调用系统接口图

6、字符设备节点介绍

7、文件拷贝实例

#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* * ./copy 1.txt 2.txt * argc = 3 * argv[0] = "./copy" * argv[1] = "1.txt" * argv[2] = "2.txt" */ int main(int argc, char **argv) { int fd_old, fd_new; struct stat stat; char *buf; /* 1. 判断参数 */ if (argc != 3) { printf("Usage: %s <old-file> <new-file>\n", argv[0]); return -1; } /* 2. 打开老文件 */ fd_old = open(argv[1], O_RDONLY); if (fd_old == -1) { printf("can not open file %s\n", argv[1]); return -1; } /* 3. 确定老文件的大小 */ if (fstat(fd_old, &stat) == -1) { printf("can not get stat of file %s\n", argv[1]); return -1; } /* 4. 映射老文件 */ buf = mmap(NULL, stat.st_size, PROT_READ, MAP_SHARED, fd_old, 0); if (buf == MAP_FAILED) { printf("can not mmap file %s\n", argv[1]); return -1; } /* 5. 创建新文件 */ fd_new = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); if (fd_new == -1) { printf("can not creat file %s\n", argv[2]); return -1; } /* 6. 写新文件 */ if (write(fd_new, buf, stat.st_size) != stat.st_size) { printf("can not write %s\n", argv[2]); return -1; } /* 5. 关闭文件 */ close(fd_old); close(fd_new); return 0; }