UNIX file system
Concept of file
The file is byte stream.
file type
- ordinary document
- Directory file: List of file names in the directory
- Special file: Device in the system, in / dev directory
Pathname
Directory operation
Related concepts
- User's home directory
- Current catalog, work catalog
Related command
- PWD (Print Working Directory)
- CD (Change Diredtory): When you use a parameter, go to the user's home directory, or CD $ HOME
- MKDIR: The newly created directory contains two items, "." indicates this is a directory, "." indicates that this is a subdirectory, which is contained in the superior parent directory.
- RMDir: can only delete empty subdirectory
- ls
LS option
- a
- r Displays all subdirectory content
- l Details. File type: - Ordinary, D catalog, C character device, B block device, p pipe. File protection mode: Owner, Group, Other.
- c
- f
- M
- p
- s represents the size of the file in units. Block size = 512 * 2 ^ n
- i Displays the inode number. File Name Storage In the directory, the other displayed information is stored in the inode table.
Operating multiple directorys
Use the -p option
MKDIR A1 / A2 / A2 Created Directory
RMDIR A1 / A2 / A3
File structure
Physical equipment, logic equipment
- Storage medium: random access, sequential access
- Randomly accessible storage media is divided into one or more storage areas, each like a separate physical device. Such storage areas are both logical devices.
- Divide a certain format on a logical device, constitutes a logical file system.
Logical file system storage structure
- Guide block
- Super block: Store the total information of the file system.
- i node table: Static information of the file is stored. A file corresponds to an I node entry.
- Data Storage Area: Access in blocks.
File system establishment
#mkfs logic_device_name blocksize Gap Blocks
Installation and uninstall of file system
Establishing a good file system is in use, you must install it into a directory. By accessing to the directory, you can access the device.
# mount logic_device_name Direcotry
# unmount logic_device_name Direcotry | Directory
In UNIX systems, all static objects (such as directories, devices) are "files" areas, with the aim of specification and simplifying the interface of the upper layer application.
The concept with "file" is "process".
Directory Structure
- The directory is a special file that stores information included in the included files and subdirectories.
- Each directory entry includes: file name (or sub-direct inscription), inode serial number
Process of accessing the file
Specify file name - "Find related inode serial number -" Access Inode Table - "Find File Location -" The data contained in the file
Catalog file
(file, inode) ----------> Inode entry -----------> Ordinary files
(file, inode) ----------> Inode entry -----------> Directory file
File operation
File name and its norm
- File name Available characters: letters, numbers, underscores, decimal points (no spaces).
- There is a difference in the case of the letters in the UNIX system.
- The meaning of the file name is not explained.
- There is no file extension in UNIX.
Touch command
effect
- Create a file;
- Modify the last change time of the file; CP copy file
CP Source Targe
CP file1 file2 ... Target-Dir
Option:
-i
-r
MV mobile file or rename
MV source dest // rename
MV Source Target-Dir // Mobile File
Note: The number of files does not change
RM delete file
Rm file1 file2
-i gives confirmation
-r Delete the directory and subdirectory, ie: Delete the entire directory structure
Note: Can't recover after deletion
ln
Take a name to the existing file.
The operation of any of the names of the file has the same effect.
Cat, PG, more display file content
Cat: Only a plain text file consisting of ASIC characters.
More: Split screen display file content.
PG: Linux is no such order
LP print file
LP file1 file2 ...
Ref: lpstat, Cancel
PR formatted output file
CUT cut part of the file
# CUT -D "" -f 1, 2 user_list // output the specified field
# CUT -C 26-30 User_list // Output The specified column range
Paste will connect files
# Paste -d: first second // Specify the separator:
