PHP creates a hard connection

PHP editor Zimo will introduce to you today how to establish a hard connection in PHP. A hard link means that multiple file names point to the same index node. When one of the files is modified, other files will also be affected. In PHP, a hard link can be created using the `link()` function. By specifying the paths of source files and target files, hard connections can be established. Hard links have certain practicality in file operations, and can easily perform multiple operations on the same file.

What is a hard link?

A hard link is a special file system pointer that points to another file. It is different from a symbolic link, which points to the file path, while a hard link points to the file itself. This means that the hard link shares the same inode (indexnode) as the original file, which is a structure stored in the file system that represents the file's metadata. Therefore, the hard link has the same name, size, and ownership as the original file.

Creating hard links in PHP

php You can use the link() function to create a hard link. This function requires two parameters:

• Target file: The file path to create a hard link.
• Linked file: If the file already exists, a hard link will be created pointing to it.

grammar:

link(string $target_file, string $link_file) : bool

return value:

• Returns true when a hard link is successfully created.
• Return false on failure.

Example:

// Create a file named "hard_link.txt" and write some data
$target_file = "hard_link.txt";
file_put_contents($target_file, "This is a test file.");

//Create a hard link to the target file named "link.txt"
$link_file = "link.txt";
link($target_file, $link_file);

// Check if two files have the same inode, indicating they are hard links
if (fileinode($target_file) === fileinode($link_file)) {
echo "Hard link created successfully.";
} else {
echo "Error creating hard link.";
}

Precautions:

• Only hard links can be created for files on different file systems.
• Unable to create a hard link to the directory.
• Changing the contents of the file associated with the hard link will also change the contents of the original file since they point to the same inode.
• Deleting a hard link will not delete the original file. Files are only deleted if the original file or all hard links are removed.
• Hard links are more efficient than symbolic links because they point directly to files, not paths, and they don't incur any overhead.

advantage:

• Save disk space because files are only stored once.
• Allows multiple naming of files for easier organization and access.
• Changing the contents of any hard link will also change the original file, which is useful in scenarios where multiple files need to be updated simultaneously.

shortcoming:

• Hard links can only be created on the same file system.
• Unable to create a hard link to the directory.
• If the original file is deleted, all hard links will become invalid.

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