readlink

What is readlink?

The readlink command is a fundamental utility in Linux that retrieves the target path of a symbolic link. It simply tells you where a symlink points to. This is for managing complex file structures and understanding the relationships between files and directories. Unlike ls -l, which shows you that a file is a symlink, readlink shows you what it points to.

Basic Usage

The simplest form of readlink is:

readlink <symlink>

Replace <symlink> with the actual path to the symbolic link. For example, if you have a symlink named mylink pointing to /home/user/documents, the command would be:

readlink mylink

This will output:

/home/user/documents

Handling Multiple Symlinks

If you encounter a chain of symbolic links (a symlink pointing to another symlink), the readlink command, by default, only resolves the immediate target.

Let’s say we have:

• mylink: points to anotherlink
• anotherlink: points to /home/user/documents

The command readlink mylink would only return:

anotherlink

To resolve all symlinks in the chain, you need the -f (or --canonicalize) option:

readlink -f mylink 

This will output:

/home/user/documents

Reading Symlinks with Null-terminated Output

For scripting purposes, you might want the output to be null-terminated instead of newline-terminated. This is particularly useful when dealing with filenames that might contain spaces or special characters. Use the -z (or --null) option:

readlink -z mylink

This will output the target path followed by a null character, which can then be processed appropriately by your script. You’ll likely use tools like xargs -0 to handle this null-separated output.

Error Handling

If you attempt to use readlink on a file that is not a symbolic link, it will usually return an error. You can check the exit status of the command to handle this gracefully in scripts. For example:

readlink myfile || echo "myfile is not a symlink"

Advanced Example: Creating and Reading Symlinks in a Script

Here’s a bash script that demonstrates creating a symlink and then reading its target using readlink:

#!/bin/bash


ln -s /tmp/myfile.txt mylink


if [ -e mylink ]; then
  # Read the target of the symlink
  target=$(readlink -f mylink)
  echo "Symlink mylink points to: $target"
else
  echo "Symlink mylink does not exist"
fi

#Remove the symlink (good practice for cleanup)
rm mylink

This script creates a symlink, checks if it exists, reads its canonical target using readlink -f, and then prints the result. Finally it removes the created symlink. Remember to create /tmp/myfile.txt before running this script.

This detailed exploration of the readlink command provides you with the tools and knowledge to effectively manage symbolic links within your Linux environment. By understanding the different options and their uses, you can write more efficient scripts and streamline your workflow.