How to use the command 'readlink' (with examples)
The readlink command is a utility commonly found in Unix-like operating systems. Its primary purpose is to follow and resolve symbolic links, often referred to as symlinks. A symlink is a type of file that acts as a reference or pointer to another file or directory. The readlink command allows users to obtain either the target of a symlink or the absolute path to a specified file, which can be especially useful for file management and scripting tasks.
Use case 1: Get the actual file to which the symlink points
Code:
readlink path/to/file
Motivation:
In many instances, when navigating a complex file system, you might encounter symbolic links. These symlinks are essentially shortcuts that point to other files or directories. However, the default file listing commands like ls might not always display where these symlinks lead. If you’re tasked with managing or auditing a system, knowing the actual file a symlink refers to is crucial to understanding the structure and flow of data across directories. This can come in handy, for example, when troubleshooting broken links or when trying to locate the origin of configuration files or executables.
Explanation:
readlink: This is the command used to identify where a symlink is pointing. It outputs the path to which the symlink refers.path/to/file: This argument specifies the path of the symlink for which you need to find the target. It’s critical that this is a symlink and not a regular file for the command to function as intended.
Example Output:
If you have a symbolic link /home/user/link_to_example pointing to /var/data/example.txt, running the command would yield:
/var/data/example.txt
This output tells you exactly which file the symlink is targeting, allowing you to proceed with any necessary actions on the actual file itself.
Use case 2: Get the absolute path to a file
Code:
readlink -f path/to/file
Motivation:
Understanding the absolute path of a file is fundamental in scripting, administration, and various programming tasks as it provides a complete and unambiguous location of a file in the directory hierarchy. This is especially crucial in environments where relative paths are commonly used, or where symlinks might lead to other symlinks, creating a complex chain of references. By resolving these links to an absolute path, users can avoid potential pitfalls associated with relative paths or deeply nested symlinks.
Explanation:
readlink: The base command to be used.-f: This option is critical. It forces the resolution of all components in the path to produce an absolute pathname. This means that not only does it follow symlinks, but it also converts relative paths into absolute ones.path/to/file: This is the file or symlink whose absolute path is needed. You just need to provide the file path as input, and the command will handle the rest.
Example Output:
Assuming the file is located at /home/user/documents/notes/, but your current working directory is /home/user and you’re using a symlink named current_link:
/home/user/documents/notes/
This output provides you with the precise path to your file, ending any confusion that might arise from navigating symlinks or ambiguous directory structures.
Conclusion:
The readlink command, though often overlooked, is immensely valuable when working within environments that extensively use symbolic links. By mastering these use cases, users can significantly increase their proficiency in file system navigation and manipulation. Whether you’re trying to trace a problematic symbolic link or you need to resolve a file’s absolute path in a script, readlink offers a straightforward solution to these common tasks.
