UNIX advanced programming files and directories

Files and directories

Realize
Ls-l

1.
Stat ();
Fstat ();
Lstat ();

2. Type of file (St_mode)
dbcpls-
D: Catalogue
B: Block device
C: Character device
P: Piping
L: Symbolic Link
S: Socket
-: Normal file

3. Permissions for files (st_mode)
Rwx
U+s:u must have x permissions, plus s permissions, so that the user who executes this file temporarily has file owner permissions
G+s:
O+t: If a directory has T permissions, it can ensure that other users can create files for this directory, but can only delete/modify their own files

4. Number of hard links to files (St_nlink)
Hard Links:
Create a hard-link file for any one file, equivalent to adding a record entry
The same inode, corresponding to two names.
Symbolic Links:
Create a symbolic link file for any file, the path of the source file is stored in the symbolic link file, and there is a separate inode

5. Owner and group of files (St_uid, St_gid)

6. Size of the file
Number of bytes in the file (st_size)
Not equal to the size of the disk space occupied
Disk minimum unit is sector (512B) (st_blocks)
File System minimum Unit is block (General 4K)

7. Time of the file
Access Time-----Last visited
Modify time-----Last modified content (LS-L)
Change time-----Last modification of the attribute information (inode)

8. Read the Catalogue
Opendir (3);
Readdir (3);
Closedir (3);

Glob (3);

9. Understand
mkdir (2);
RmDir (2);

Remove (3);//unlink (2)/rmdir (2);
Rename (2);

Chown (2);
Fchown (2);
Lchown (2);

Umask (2);
chmod (2);
Fchmod (2);

Link (2);
Unlink (2);

System data files and information

1./etc/passwd
Mans 5 passwd

Getpwuid (3);
Getpwnam (3);

2./etc/group
Mans 5 Group

Getgrgid (3);
Getgrnam (3);

3./etc/shadow
Mans 5 Shadow

Getspnam (3);
Crypt (3);
Getpass (3);

4. Time Routines
Time (2);//timestamp
Gmtime (3);
LocalTime (3);
Strftime (3);
Mktime (3);

CTime (3);

UNIX advanced programming files and directories