文件系统：目录与文件
This commit is contained in:
lzy
@@ -1,3 +1,15 @@
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# 目录
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- [目录](#目录)
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- [数据结构](#数据结构)
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- [架构梳理](#架构梳理)
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- [静态库与动态库](#静态库与动态库)
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- [静态库](#静态库)
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- [以链式双向链表的`lib2`为例。](#以链式双向链表的lib2为例)
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- [动态库](#动态库)
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- [还是以`lib2`为例。](#还是以lib2为例)
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- [以链式存储栈为例，`libstack`依赖`libllist`。](#以链式存储栈为例libstack依赖libllist)
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# 数据结构
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## 架构梳理
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@@ -162,6 +162,7 @@ int setvbuf(FILE *stream, char *buf, int mode, size_t size);
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*
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* !!! 里面有 malloc 动作，未释放
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* !!! 是方言，可以自己封装一个mygetline和mygetline_free
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* !!! 但是根据chatgpt，好像直接 free(*lineptr) 就行了
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*
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*/
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ssize_t getline(char **lineptr, size_t *n, FILE *stream);
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@@ -260,6 +261,77 @@ off_t lseek(int fd, offt offset, int whence);
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### IO的效率问题
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习题：将`mycpy.c`程序进行更改，将`BUFSIZE`的值放大，观察进程消耗的时间，注意性能出现拐点的值以及程序何时段错误。
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解答：
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将`BUFSIZE`作为命令行参数传入，`int bufsize = atoi(argv[3]);`
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通过脚本进行试验：
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```bash
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#!/bin/bash
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# 生成一个 5GB 的文件
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dd if=/dev/urandom of=/tmp/bigfile bs=1G count=5
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# 输入和输出文件的路径
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src="/tmp/bigfile"
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dst="/tmp/outfile"
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# 编译你的程序
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gcc -o mycpy_bufsize mycpy_bufsize.c
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# 初始化 BUFSIZE
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bufsize=512
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# 循环，每次 BUFSIZE * 2
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while true; do
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# 用 time 命令运行你的程序，并将结果重定向到一个临时文件
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{ time ./mycpy_bufsize $src $dst $bufsize; } 2> time.txt
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# 检查程序的退出状态
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if [ $? -ne 0 ]; then
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echo "Max BUFSIZE before segfault: $bufsize"
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break
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fi
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# 提取 time 的结果
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real_time=$(grep real time.txt | awk -F' ' '{print $2}')
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user_time=$(grep user time.txt | awk -F' ' '{print $2}')
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sys_time=$(grep sys time.txt | awk -F' ' '{print $2}')
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# 输出 BUFSIZE 和 time 的结果
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echo "BUFSIZE: $bufsize, Real Time: $real_time, User Time: $user_time, Sys Time: $sys_time"
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# BUFSIZE * 2
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bufsize=$((bufsize * 2))
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done
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# 删除临时文件
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rm time.txt
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rm $src
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rm $dst
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```
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结果：
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```bash
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wan@SK-20240106UQUX:~/Linux-C-Notes/C13-Linux系统编程/io/sys$ ./time.sh
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BUFSIZE: 512, Real Time: 0m7.672s, User Time: 0m0.650s, Sys Time: 0m7.007s
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BUFSIZE: 1024, Real Time: 0m5.026s, User Time: 0m0.201s, Sys Time: 0m4.651s
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BUFSIZE: 2048, Real Time: 0m3.535s, User Time: 0m0.158s, Sys Time: 0m3.183s
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BUFSIZE: 4096, Real Time: 0m2.418s, User Time: 0m0.059s, Sys Time: 0m2.232s
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BUFSIZE: 8192, Real Time: 0m2.363s, User Time: 0m0.040s, Sys Time: 0m2.150s
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BUFSIZE: 16384, Real Time: 0m2.279s, User Time: 0m0.030s, Sys Time: 0m2.079s
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BUFSIZE: 32768, Real Time: 0m2.238s, User Time: 0m0.020s, Sys Time: 0m2.026s
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BUFSIZE: 65536, Real Time: 0m2.114s, User Time: 0m0.000s, Sys Time: 0m1.972s
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BUFSIZE: 131072, Real Time: 0m2.302s, User Time: 0m0.019s, Sys Time: 0m1.982s
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BUFSIZE: 262144, Real Time: 0m2.244s, User Time: 0m0.000s, Sys Time: 0m2.016s
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BUFSIZE: 524288, Real Time: 0m2.254s, User Time: 0m0.000s, Sys Time: 0m2.039s
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BUFSIZE: 1048576, Real Time: 0m2.249s, User Time: 0m0.010s, Sys Time: 0m2.037s
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BUFSIZE: 2097152, Real Time: 0m2.304s, User Time: 0m0.000s, Sys Time: 0m2.108s
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BUFSIZE: 4194304, Real Time: 0m2.234s, User Time: 0m0.010s, Sys Time: 0m2.082s
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Max BUFSIZE before segfault: 8388608
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```
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在`ulimit -a`中，我的系统的`stack size`是`8192`，所以`BUFSIZE`不能超过`8192`，否则会段错误。与测试结果一致。
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### 文件共享
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多个任务共同操作一个文件或者协同完成任务
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@@ -325,3 +397,262 @@ int ioctl(int fd, unsigned long request, ... /* arg */);
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### /dev/fd/目录
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**虚目录**：显示当前进程的文件描述符信息
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# 文件系统
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类`ls`的实现，如`myls -l -a -i -n`
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`cmd --长格式 -短格式 非选项的传参`
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## 目录和文件
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1. 获取文件属性
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```c
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/**
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* 将文件的属性存储到buf中
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* stat : 通过文件路径获取属性，面对符号链接文件时，
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* 获取的是指向的目标文件的属性
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* fstat: 通过文件描述符获取属性
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* lstat: 通过文件路径获取属性，面对符号链接文件时，
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*/
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int stat(const char *path, struct stat *buf);
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int fstat(int fd, struct stat *buf);
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int lstat(const char *path, struct stat *buf);
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struct stat {
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dev_t st_dev; /* ID of device containing file */
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ino_t st_ino; /* inode number */
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// 文件唯一标识，身份证号
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mode_t st_mode; /* protection */
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// st_mode: 文件权限+文件类型
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// 文件权限
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// 七种文件类型：dcb-lsp
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nlink_t st_nlink; /* number of hard links */
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uid_t st_uid; /* user ID of owner */
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gid_t st_gid; /* group ID of owner */
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dev_t st_rdev; /* device ID (if special file) */
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off_t st_size; /* total size, in bytes */
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// 在linux下，与windows不同，size值仅仅是属性
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// 不能实际体现占用磁盘大小，详见 big.c
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blksize_t st_blksize; /* blocksize for file system I/O */
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blkcnt_t st_blocks; /* number of 512B blocks allocated */
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time_t st_atime; /* time of last access */
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time_t st_mtime; /* time of last modification */
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time_t st_ctime; /* time of last status change */
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};
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```
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2. 文件访问权限
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`st_mode`是一个16位的二进制数，文件类型，文件权限，特殊权限。
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3. `umask`
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作用：防止产生权限过松的文件。
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`0666 &~umask`
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`umask`也是一个终端命令，可以查看和设置。
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`mode_t umask(mode_t mask);`
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4. 文件权限的更改/管理
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```c
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/**
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* 更改文件权限
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*/
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int chmod(const char *path, mode_t mode);
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int fchmod(int fd, mode_t mode);
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```
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5. 粘住位
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t位，例如`/tmp`目录。
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6. 文件系统：`FAT`, `UFS`
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文件或数据的存储格式。
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- `FAT`：静态存储的单链表
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```c
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struct node_st{
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int next[N];
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char data[N][SIZE];
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};
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```
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- `UFS`：
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缺点：不善于处理大量的小文件，因为每个文件都有一个`inode`，占用空间。
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> 面试题：
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> 不用比较，比较两个uint32_t的大小
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> 使用位图
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7. 硬链接，符号链接
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- 硬链接
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`ln bigfile bigfile_link`
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与目录项是同义词
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相当于目录项又弄了一份，使用`ls -i`可以看到`inode`号相同。
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限制：不能给分区建立，不能给目录建立
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- 符号链接
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`ln -s bigfile_link bigfile_s`
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优点：可以跨分区，可以给目录建立
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```c
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int link(const char *oldpath, const char *newpath);
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/**
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* 只有没有引用的数据才会真正删除
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* 可以利用这一点创建匿名文件
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*/
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int unlink(const char *pathname);
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int remove(const char *pathname);
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/**
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* 改变文件的路径或者名字
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*/
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int rename(const char *oldpath, const char *newpath);
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```
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8. `utime`
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```c
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/**
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* 更改文件最后读/写的时间
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*/
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int utime(const char *filename, const struct utimbuf *times);
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struct utimbuf {
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time_t actime; /* access time */
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time_t modtime; /* modification time */
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};
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struct time_t {
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long tv_sec; /* seconds */
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long tv_usec; /* microseconds */
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};
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```
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9. 目录的创建和销毁
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`mkdir, rmdir`
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```c
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int mkdir(const char *pathname, mode_t mode);
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/**
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* 只有目录为空才能删除
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*/
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int rmdir(const char *pathname);
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```
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10. 更改当前工作路径
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`cd, pwd`
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```c
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/**
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* 改变当前工作路径
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* 可以突破假根目录
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* 但是不能突破chroot
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*/
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int chdir(const char *path);
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int fchdir(int fd);
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/**
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* 获取当前工作路径
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*/
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long getcwd(char *buf, unsigned long size);
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```
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11. 分析目录/读取目录内容
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```c
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/**
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* 法一
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* 解析模式/通配符
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*
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* @prarm: pattern 匹配模式
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* @prarm: flags 匹配标志
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* @prarm: errfunc 错误回调函数
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* @prarm: pglob 匹配结果
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*
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* @return 匹配的文件数量
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*/
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int glob(const char *restrict pattern, int flags,
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int (*errfunc)(const char *epath, int eerrno),
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glob_t *restrict pglob);
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/**
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* 释放glob_t结构体
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*/
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void globfree(glob_t *pglob);
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/**
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* 与argc, argv类似
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*/
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typedef struct {
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size_t gl_pathc; /* Count of paths matched so far */
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char **gl_pathv; /* List of matched pathnames */
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size_t gl_offs; /* Slots to reserve in gl_pathv */
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} glob_t;
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/**
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* 法二
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*/
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/**
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* 打开一个目录
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* 返回一个指向DIR结构体的指针
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* 是堆区，需要 closedir 释放
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*/
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DIR *opendir(const char *name);
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DIR *fdopendir(int fd);
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/**
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* 关闭一个目录
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*/
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int closedir(DIR *dirp);
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/**
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* 读取一个目录
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*
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* 返回指针指向静态区
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*/
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struct dirent *readdir(DIR *dirp);
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int readdir_r(DIR *restrict dirp,
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struct dirent *restrict entry,
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struct dirent **restrict result);
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struct dirent {
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ino_t d_ino; /* inode number */
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off_t d_off; /* offset to the next dirent */
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unsigned short d_reclen; /* length of this record */
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unsigned char d_type; /* type of file; not supported
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by all file system types */
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char d_name[256]; /* filename */
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};
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/**
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* 重置一个目录
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*/
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void rewinddir(DIR *dirp);
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void seekdir(DIR *dirp, long offset);
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long telldir(DIR *dirp);
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/**
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* du 命令
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* 以字节为单位，统计目录下所有文件的大小
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*
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*/
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```
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作业：用另一套函数实现`mydu`
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## 系统数据文件和信息
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## 进程环境
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34
C13-Linux系统编程/fs/big.c
Normal file
34
C13-Linux系统编程/fs/big.c
Normal file
@@ -0,0 +1,34 @@
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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int main(int argc, char **argv)
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{
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if (argc < 2)
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{
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fprintf(stderr, "Usage:...\n");
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exit(1);
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}
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int fd;
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fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0600);
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if (fd < 0)
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{
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perror("open()");
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exit(1);
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}
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// 生成一个5G的文件
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// !!! 整数溢出
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lseek(fd, 5LL * 1024LL * 1024LL * 1024LL - 1LL, SEEK_SET);
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// 写入尾0
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write(fd, "", 1);
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close(fd);
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exit(0);
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}
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41
C13-Linux系统编程/fs/flen.c
Normal file
41
C13-Linux系统编程/fs/flen.c
Normal file
@@ -0,0 +1,41 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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// !!! 不是int
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static off_t flen(char *fname)
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{
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struct stat statres;
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if (stat(fname, &statres) < 0)
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{
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perror("stat()");
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exit(1);
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}
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return statres.st_size;
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}
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/**
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* @brief 获取文件大小
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* @details
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* Usage: ./flen filename
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*
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* @param argc
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* @param argv
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* @return int
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*/
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int main(int argc, char **argv)
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{
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if (argc < 2)
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{
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fprintf(stderr, "Usage:...\n");
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exit(1);
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}
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// !!! 通过makefile指定off_t 64位
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printf("%lld\n", flen(argv[1]));
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exit(0);
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}
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54
C13-Linux系统编程/fs/ftype.c
Normal file
54
C13-Linux系统编程/fs/ftype.c
Normal file
@@ -0,0 +1,54 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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static int ftype(const char *fname)
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{
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struct stat statres;
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if (stat(fname, &statres) < 0)
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{
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perror("stat()");
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exit(1);
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}
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if (S_ISREG(statres.st_mode))
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return '-';
|
||||
else if (S_ISDIR(statres.st_mode))
|
||||
return 'd';
|
||||
else if (S_ISSOCK(statres.st_mode))
|
||||
return 's';
|
||||
else if (S_ISFIFO(statres.st_mode))
|
||||
return 'p';
|
||||
else if (S_ISBLK(statres.st_mode))
|
||||
return 'b';
|
||||
else if (S_ISCHR(statres.st_mode))
|
||||
return 'c';
|
||||
else if (S_ISLNK(statres.st_mode))
|
||||
return 'l';
|
||||
else
|
||||
return '?';
|
||||
}
|
||||
|
||||
/**
|
||||
* @brief 获取文件类型
|
||||
* @details
|
||||
* Usage: ftype <filename>
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
if (argc < 2)
|
||||
{
|
||||
fprintf(stderr, "Usage:...\n");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
printf("%c\n", ftype(argv[1]));
|
||||
|
||||
exit(0);
|
||||
}
|
||||
46
C13-Linux系统编程/fs/glob.c
Normal file
46
C13-Linux系统编程/fs/glob.c
Normal file
@@ -0,0 +1,46 @@
|
||||
#include <glob.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
|
||||
// #define PAT "/etc/a*.conf"
|
||||
#define PAT "/etc/*" // 不包括隐藏文件 .*
|
||||
|
||||
#if 0
|
||||
static int errfunc_(const char *errpath, int eerrno)
|
||||
{
|
||||
puts(errpath);
|
||||
fprintf(stderr, "ERROR MSG: %s\n", strerror(eerrno));
|
||||
return 0;
|
||||
}
|
||||
#endif
|
||||
|
||||
/**
|
||||
* @brief ls /etc/a*.conf
|
||||
* @details
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
glob_t globres;
|
||||
int err;
|
||||
|
||||
err = glob(PAT, 0, NULL, &globres);
|
||||
if (err)
|
||||
{
|
||||
printf("ERROR CODE = %d\n", err);
|
||||
exit(1);
|
||||
}
|
||||
|
||||
for (int i = 0; i < globres.gl_pathc; i++)
|
||||
{
|
||||
puts(globres.gl_pathv[i]);
|
||||
}
|
||||
|
||||
// !!!
|
||||
globfree(&globres);
|
||||
exit(0);
|
||||
}
|
||||
15
C13-Linux系统编程/fs/main.c
Normal file
15
C13-Linux系统编程/fs/main.c
Normal file
@@ -0,0 +1,15 @@
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
printf("argc = %d\n", argc);
|
||||
|
||||
// for (int i = 0; i < argc; i++)
|
||||
for (int i = 0; argv[i] != NULL; i++)
|
||||
{
|
||||
puts(argv[i]);
|
||||
}
|
||||
|
||||
exit(0);
|
||||
}
|
||||
125
C13-Linux系统编程/fs/mydu.c
Normal file
125
C13-Linux系统编程/fs/mydu.c
Normal file
@@ -0,0 +1,125 @@
|
||||
#include <glob.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <string.h>
|
||||
#include <sys/stat.h>
|
||||
#include <sys/types.h>
|
||||
|
||||
#define PATHSIZE 1024
|
||||
|
||||
static int path_noloop(const char *path)
|
||||
{
|
||||
char *pos;
|
||||
|
||||
/**
|
||||
* @brief strrchr
|
||||
* @details
|
||||
*
|
||||
* 找到 path 中最后一个 '/' 字符的位置
|
||||
*/
|
||||
pos = strrchr(path, '/');
|
||||
if (NULL == pos)
|
||||
exit(1);
|
||||
|
||||
if ((0 == strcmp(pos + 1, ".") || 0 == strcmp(pos + 1, "..")))
|
||||
return 0;
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int64_t mydu(const char *path)
|
||||
{
|
||||
// 优化递归
|
||||
// 将部分与递归无关的变量拿出栈，用 static 修饰
|
||||
static struct stat statres;
|
||||
static char nextpath[PATHSIZE];
|
||||
glob_t globres;
|
||||
int64_t sum;
|
||||
int i;
|
||||
|
||||
if (lstat(path, &statres) < 0)
|
||||
{
|
||||
perror("lstat()");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
if (!S_ISDIR(statres.st_mode))
|
||||
{
|
||||
/* 非目录 */
|
||||
return statres.st_blocks;
|
||||
/*
|
||||
* st_blocks 代表磁盘块数量，一个磁盘块大小为512字节
|
||||
* 所以除以2才表示多少个1k字节
|
||||
*/
|
||||
}
|
||||
|
||||
/* 目录 */
|
||||
/* 例如：/aaa/bbb/ccc/ddd/eee/fff */
|
||||
|
||||
strncpy(nextpath, path, PATHSIZE);
|
||||
strncat(nextpath, "/*", PATHSIZE); //[W]
|
||||
// if (glob(nextpath, 0, NULL, &globres))
|
||||
// {
|
||||
// perror("glob(), 1");
|
||||
// exit(1);
|
||||
// }
|
||||
glob(nextpath, 0, NULL, &globres);
|
||||
|
||||
// !!! 要考虑 . 和 .. 目录
|
||||
strncpy(nextpath, path, PATHSIZE);
|
||||
strncat(nextpath, "/.*", PATHSIZE); //[W]
|
||||
/*
|
||||
* 这个警告是因为 strncat 函数的第三个参数（即 PATHSIZE）等于目标字符串
|
||||
* nextpath 的大小。这可能会导致 nextpath 缓冲区溢出，因为 strncat
|
||||
* 函数会在目标字符串的末尾添加一个 null 字符（'\0'）。
|
||||
*/
|
||||
|
||||
// !!! APPEND
|
||||
// if (glob(nextpath, GLOB_APPEND, NULL, &globres))
|
||||
// {
|
||||
// perror("glob(), APPEND");
|
||||
// exit(1);
|
||||
// }
|
||||
glob(nextpath, GLOB_APPEND, NULL, &globres);
|
||||
|
||||
sum = statres.st_blocks;
|
||||
|
||||
for (i = 0; i < globres.gl_pathc; i++)
|
||||
{
|
||||
if (path_noloop(globres.gl_pathv[i]))
|
||||
{
|
||||
sum += mydu(globres.gl_pathv[i]);
|
||||
}
|
||||
}
|
||||
|
||||
// !!!
|
||||
globfree(&globres);
|
||||
return sum;
|
||||
}
|
||||
|
||||
/**
|
||||
* @brief mydu
|
||||
* @details
|
||||
* Usage: mydu [FILE]...
|
||||
*
|
||||
* 用到了递归的思想
|
||||
*
|
||||
* !!! 未考虑权限问题
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
if (argc < 2)
|
||||
{
|
||||
fprintf(stderr, "Usage: mydu [FILE]...\n");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
printf("%lld\n", mydu(argv[1]) / 2);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
38
C13-Linux系统编程/fs/readdir.c
Normal file
38
C13-Linux系统编程/fs/readdir.c
Normal file
@@ -0,0 +1,38 @@
|
||||
#include <dirent.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <sys/types.h>
|
||||
|
||||
#define PAT "/etc"
|
||||
|
||||
/**
|
||||
* @brief 解析PAT下文件个数
|
||||
* @details
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
DIR *dp;
|
||||
struct dirent *cur;
|
||||
|
||||
dp = opendir(PAT);
|
||||
if (NULL == dp)
|
||||
{
|
||||
perror("opendir()");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
// !!! 注意括号
|
||||
while ((cur = readdir(dp)) != NULL)
|
||||
{
|
||||
puts(cur->d_name);
|
||||
}
|
||||
|
||||
closedir(dp);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
@@ -35,6 +35,9 @@ int main(int argc, char **argv)
|
||||
// 修改后发现，linesize初始值就是120，是后面不够再增加
|
||||
}
|
||||
|
||||
// !!!
|
||||
free(linebuf);
|
||||
|
||||
fclose(fp);
|
||||
exit(0);
|
||||
}
|
||||
77
C13-Linux系统编程/io/sys/mycpy_bufsize.c
Normal file
77
C13-Linux系统编程/io/sys/mycpy_bufsize.c
Normal file
@@ -0,0 +1,77 @@
|
||||
#include <fcntl.h>
|
||||
#include <stdio.h>
|
||||
#include <stdlib.h>
|
||||
#include <unistd.h>
|
||||
|
||||
|
||||
/**
|
||||
* @brief
|
||||
* @details
|
||||
* Usage: mycpy <src> <dst> <bufsize>
|
||||
*
|
||||
* @param argc
|
||||
* @param argv
|
||||
*
|
||||
* @return int
|
||||
*/
|
||||
int main(int argc, char **argv)
|
||||
{
|
||||
if (argc < 4)
|
||||
{
|
||||
fprintf(stderr, "Usage: %s <src> <dst> <bufsize>\n", argv[0]);
|
||||
exit(1);
|
||||
}
|
||||
|
||||
int bufsize = atoi(argv[3]);
|
||||
|
||||
int sfd, dfd;
|
||||
char buf[bufsize];
|
||||
int len, ret, pos;
|
||||
|
||||
sfd = open(argv[1], O_RDONLY);
|
||||
if (sfd < 0)
|
||||
{
|
||||
perror("open");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
dfd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0600);
|
||||
if (dfd < 0)
|
||||
{
|
||||
// !!!
|
||||
close(sfd);
|
||||
perror("open");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
while (1)
|
||||
{
|
||||
len = read(sfd, buf, bufsize);
|
||||
if (len < 0)
|
||||
{
|
||||
perror("read");
|
||||
break;
|
||||
}
|
||||
if (len == 0)
|
||||
break;
|
||||
|
||||
pos = 0;
|
||||
while (len > 0)
|
||||
{
|
||||
/* 可能没写完被别的中断打断 */
|
||||
ret = write(dfd, buf + pos, len);
|
||||
if (ret < 0)
|
||||
{
|
||||
perror("write");
|
||||
exit(1);
|
||||
}
|
||||
pos += ret;
|
||||
len -= ret;
|
||||
}
|
||||
}
|
||||
|
||||
close(dfd);
|
||||
close(sfd);
|
||||
|
||||
exit(0);
|
||||
}
|
||||
Reference in New Issue
Block a user