1、ls产生一个文件名的列表，它大致是这样工作的：

open directory+-> read entry        - end of dir? -+|__ display file info                |    close directory   <--------------+

2、目录是一种特殊的文件，它的内容是文件和目录的名字。与普通文件不同的是，目录文件永远不会空，每个目录至少包含2个特殊的项，即 “.”和“..”，其中 “.”不是当前目录，“..”表示上一级目录。

3、man 3 readdir

#include 
    
     #include 
     
      DIR *opendir(const char *dir_name);struct dirent *readdir(DIR *dir_name);int readdir_r(DIR *dir_ptr, struct dirent *entry,    struct dirent **result);long telldir(DIR *dir_ptr);void seekdir(DIR *dir_ptr, long location);void rewinddir(DIR *dir_ptr);int closedir(DIR *dir_ptr);
     
    

4、ls的算法：

main()    opendir    while (readdir)        print d_name    closedir

5、用stat得到文件信息：

man 2 stat

#include 
    
     int res = stat(const char *path, struct stat *buf);    /* return 0 for success, -1 for error */
    

struct stat {    dev_t     st_dev;     /* ID of device containing file */    ino_t     st_ino;     /* inode number */    mode_t    st_mode;    /* protection */    nlink_t   st_nlink;   /* number of hard links */    uid_t     st_uid;     /* user ID of owner */    gid_t     st_gid;     /* group ID of owner */    dev_t     st_rdev;    /* device ID (if special file) */    off_t     st_size;    /* total size, in bytes */    blksize_t st_blksize; /* blocksize for filesystem I/O */    blkcnt_t  st_blocks;  /* number of 512B blocks allocated */    time_t    st_atime;   /* time of last access */    time_t    st_mtime;   /* time of last modification */    time_t    st_ctime;   /* time of last status change */};

6、man getpwuid

7、SUID 位告诉内核，运行这个程序的时候认为是由文件所有者在运行这个程序；SGID位告诉内核，运行这个程序的时候认为文件所属的组在运行这个程序；sticky位对于文件，在早期用于交换（swap）技术，对于目录而言被设计用来存放临时文件，如/tmp。

ls -l sample-rwsr-sr-t   1   root root 2345    Jul 24 00:45    sample

8、设置和修改文件的属性

#include 
    
     #include 
     
      int res = chmod(const char *path, mod_t mode);int res = chmod(int fd, mode_t mode);    /* On success, 0 is returned. On error, -1 is returned       and errno is set appropriately */
     
    

#include 
    
     int chown(const char *path, uid_t owner, gid_t group);int fchown(int fd, uid_t owner, gid_t group);int lchown(const char *path, uid_t owner, gid_t group);    /* On success, 0 is returned. On error, -1 is returned       and errno is set appropriately */
    

9、修改最后修改时间和最后访问时间:

man utime

10、修改文件名

man 2 rename