1.依賴的頭文件

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

2.函數定義：

//通過傳入文件路徑，struct stat結構體指針的方式

int stat(const char *path, struct stat *buf);

//通過文件描述符獲取文件對應的屬性。文件打開后這樣操作
int fstat(int fd, struct stat *buf);

//通過文件描述符獲取文件對應的屬性。文件打開后這樣操作
int lstat(const char *path, struct stat *buf);

說明：執行成功返回0，失敗返回-1，錯誤代碼存于errno

注意：

?????????給定一個path

?????????A:stat函數返回一個與此命名文件有關的信息結構

?????????B:fstat函數獲得已在描述符filedes上打開的文件信息

?????????C:lstat函數類似于stat，但是當命名的文件時一個符號連接是，lstat返回該符號連接的有關信息，而不是由此符號鏈接引用的文件的信息

3.這些函數的功能是返回關于一個文件的信息；

???A:stat既有命令也有同名函數，用來獲取文件的Inode里主要信息，stat跟蹤符號鏈接

?? B:lstat不跟蹤符號鏈接

4.stat里面時間辨析

???atime(最近訪問時間)

???mtime(最近更改時間)：指最近修改文件內容的時間

???ctime(最近改動時間)：指最近改動Innode的時間，要注意的是mtime信息是Innode中的一項，所以一旦它修改了，這一項也會修改

5.所有的這些系統調用后返回一個stat的結構體，這個結構體包括以下內容：

struct stat {
?????????????? dev_t???? st_dev;???????? /* ID of device containing file???文件設備編號*/
?????????????? ino_t???? st_ino;???????????/* inode number??節點號*/
?????????????? mode_t??? st_mode;??? /* protection??文件的類型和存取的權限*/
?????????????? nlink_t?? st_nlink;??????? /* number of hard links??連到該文件的硬連接數目，剛建立的文件值為1*/
?????????????? uid_t???? st_uid;?????????? /* user ID of owner???用戶ID*/
?????????????? gid_t???? st_gid;?????????? /* group ID of owner?組ID*/
?????????????? dev_t???? st_rdev;??????? /* device ID (if special file)??（設備類型）若此文件尾設備文件，則為其設備編號*/
?????????????? off_t???? st_size;????????? /* total size, in bytes??文件字節數（文件大小）*/
?????????????? blksize_t st_blksize;? /* blocksize for filesystem I/O???塊大小（文件系統的I/O緩沖區大小），類型為unsigned long類型*/
?????????????? blkcnt_t? st_blocks;?? /* number of 512B blocks allocated? ，分配的512字節的塊數，類型為unsigned long類型*/
?????????????? time_t??? st_atime;??? ?/* time of last access?最后一個訪問時間*/
?????????????? time_t??? st_mtime;??? /* time of last modification?最后更改的時間*/
?????????????? time_t??? st_ctime;???? /* time of last status change???inode的更改時間*/
?????????? };

6.通過下面的宏（macros）定義文件類型，下面的st_mode域包括以下幾個部分：

?????????? S_ISREG(m)? is it a regular file?????????????????????????????????????? 是否是一個常規文件

?????????? S_ISDIR(m)? directory???????????????????????????????????????????????????? 是否是一個目錄

?????????? S_ISCHR(m)? character device?????????????????????????????????????? 是否是一個字符設備

?????????? S_ISBLK(m)? block device?????????????????????????????????????????????? 是否是一個塊設備

?????????? S_ISFIFO(m) FIFO (named pipe)????????????????????????????????????是否是輸入輸出（管道）???

?????????? S_ISLNK(m)? symbolic link?? (Not in POSIX.1-1996.)??????是否是符號鏈接

?????????? S_ISSOCK(m) socket?? (Not in POSIX.1-1996.)??????????????是否是socket

7.下面的flags為了這個st_mode域而定義的

?????????? S_IFMT???? 0170000?? bit mask for the file type bit fields???為bit域定義的位元掩碼
?????????? S_IFSOCK?? 0140000?? socket??????????????????????????????????????????socket????????????????????????????????????????????????????????
?????????? S_IFLNK??? 0120000?? symbolic link??????????????????????????????????符號連接
?????????? S_IFREG??? 0100000?? regular file?????????????????????????????????????常規文件
?????????? S_IFBLK??? 0060000?? block device???????????????????????????????????塊設備
?????????? S_IFDIR??? 0040000?? directory??????????????????????????????????????????目錄
?????????? S_IFCHR??? 0020000?? character device????????????????????????????字符設備
?????????? S_IFIFO??? 0010000?? FIFO????????????????????????????????????????????????先進先出

?????????? S_ISUID??? 0004000?? set-user-ID bit?????????????????????????????????文件的（set user-id on execution）位
?????????? S_ISGID??? 0002000?? set-group-ID bit (see below)???????????文件的（set group-id on execution）位
?????????? S_ISVTX??? 0001000?? sticky bit (see below)????????????????????? 文件的sticky為

?????????? S_IRWXU??? 00700???? mask for file owner permissions?????文件擁有者的掩碼
?????????? S_IRUSR??? 00400???? owner has read permission?????????????擁有者有讀權限
?????????? S_IWUSR??? 00200???? owner has write permission????????????擁有者有寫權限
?????????? S_IXUSR??? 00100???? owner has execute permission????????擁有者有執行權限

?????????? S_IRWXG??? 00070???? mask for group permissions???????????組權限的掩碼??????????
?????????? S_IRGRP??? 00040???? group has read permission?????????????組有讀權限

?????????? S_IWGRP??? 00020???? group has write permission????????????組有些權限
?????????? S_IXGRP??? 00010???? group has execute permission????????組有執行權限

?????????? S_IRWXO??? 00007???? mask for permissions for others (not in group)??????其它者（不在組中）的權限掩碼
?????????? S_IROTH??? 00004???? others have read permission??????????????????????????????????其它者有讀權限
?????????? S_IWOTH??? 00002???? others have write permission???????????????????????????????? 其它者有寫權限
?????????? S_IXOTH??? 00001???? others have execute permission?????????????????????????????其它者有執行權限

8.關于黏住位

??????????若一個目錄具有sticky位（S_ISVTX）?則表示在此目錄下的文件只能被文件所有者，次目錄的所有者或者root來刪除或修改

9.此外

struct statfs {
??? long??? f_type;?????????? //文件系統類型
??? long??? f_bsize;?????????//塊大小
??? long??? f_blocks;???????//塊多少
??? long??? f_bfree;???????? //空閑的塊
??? long??? f_bavail;??????? //可用塊
??? long??? f_files;?????????? //總文件節點
??? long??? f_ffree;????????? //空閑文件節點
??? fsid_t f_fsid;???????????? //文件系統id
??? long??? f_namelen;??? //文件名的最大長度
??? long??? f_spare[6];?????//spare for later
};

10.stat（）函數調用案例（通過程序的方式調用stat(),并且呈現?stat?結構體中的信息 ）

運行結果：

總結

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