Explore the meaning and characteristics of i-node numbers in Linux

i node (inode) is a very important concept in the Linux file system, used to store metadata information of files and directories. In the file system, each file or directory corresponds to a unique i node, through which the storage location and attributes of file data can be located and managed.

1. The meaning and function of i node

i node is actually the abbreviation of index node, which saves the permissions, owner, size, and creation time of the file or directory , modification time, and the location of the actual data stored on the disk. When we create a file or directory, the system allocates a new i-node and saves the file's metadata information in the i-node, while the file's data is stored in data blocks on the disk.

2. Characteristics of i-node

(1) The i-node number is an internal identifier of the file system and is used to uniquely identify different files or directories. In common Linux file systems such as Ext2, Ext3 and Ext4, each i-node has a unique number, and the metadata information of the file can be found through the i-node number.

(2) The i node is a fixed-size data structure, usually 128 bytes or 256 bytes, which contains various attribute information of the file. Since the size of the i-node is fixed, the system needs to allocate a fixed-size i-node to store the file's metadata when the file is created.

3. Use code examples to explore i-node numbers

The following is a simple code example to demonstrate how to obtain the i-node number of a file in a Linux system and use the i-node number to query the file's i-node number. Property information:

#!/bin/bash

filename="example.txt"

# Get the i-node number of the file
inode=$(ls -i $filename | cut -d ' ' -f 1)

echo "The i-node number of file $filename is: $inode"

# Use the inode number to query the attribute information of the file
stat /proc/$$/fd/0 --printf="User to whom the file belongs: %U
File size: %s bytes
Last modified time: %y
Last access time: %x
"

In the above code example, the i-node number of the file "example.txt" is first obtained, and then the stat command is used to query the attribute information of the file through the i-node number. Among them, %U represents the user to whom the file belongs, %s represents the file size, %y represents the last modification time, and %x represents the previous visit time.

Conclusion

Through the exploration of this article, we understand the meaning and characteristics of the i-node number in Linux, and how to obtain and utilize the i-node number of the file through code examples. The i-node plays an important role in the entire file system and is one of the foundations of file management and data access. For developers, understanding the concept and usage of i-nodes can better manage and optimize the file system.

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