[Linux] Display the Target of Symbolic Links with the readlink Command

Overview

The readlink command is used to find the “actual file path” that a symbolic link (shortcut) points to. While you can check a link’s target with ls -l, readlink is better for shell scripts because it outputs only the path itself. By using the -f option, you can follow multiple layers of links and convert relative paths into full absolute paths.

Specifications (Arguments and Options)

Syntax

readlink [options] filename

Main Arguments and Options

Option	Description
-f	Follows all links recursively and outputs the full absolute path (canonicalize).
-e	Like -f, but all parts of the path must actually exist on the system.
-m	Like -f, but does not check if the file or directory actually exists.
-n	Do not output the trailing newline character.
-z	Use a null character (\0) at the end of the output instead of a newline.
-q, -s	Quiet mode; do not display error messages.

Basic Usage

When used without options, it shows the path stored in the symbolic link. If it is a relative path, it will display it as-is.

Command

# Check where the symbolic link "current_app" points to
readlink current_app

Execution Result

./versions/v1.0.2

Practical Commands

Resolve Nested Links and Get Absolute Paths

If a link points to another link (nested links) or uses a relative path, the -f option allows you to get the final absolute path immediately. This is the most common use case.

# Find the final actual path of /usr/bin/editor
# Example: editor -> /etc/alternatives/editor -> /usr/bin/vim.basic
readlink -f /usr/bin/editor

Output:

/usr/bin/vim.basic

Verify Link Targets (For Scripts)

The -e option returns an exit status of 1 (failure) if the target file does not exist (broken link). You can use this to check if a link is valid before running a process.

# Check if the target of the link exists
# For a valid link:
readlink -e /usr/bin/python3
echo "Status: $?"

# For a broken link or non-existent file:
readlink -e /usr/bin/invalid_link
echo "Status: $?"

Output:

/usr/bin/python3.10
Status: 0

Status: 1

Note: If the status is 1, the command produces no text output.

Customization Points

• Absolute Path Conversion: If you provide a normal file instead of a symbolic link, readlink -f will return the full absolute path of that file.
• Shell Scripting: This command works well with variable assignment. You can normalize paths using REAL_PATH=$(readlink -f "$TARGET_FILE").

Important Notes

• macOS (BSD) Differences: The version of readlink in Linux (GNU) and macOS (BSD) behave differently. The BSD version often lacks the -f option. For scripts that need to work on both, consider using the realpath command instead.
• Choosing between -f and -m: If you want to find the absolute path for a file or directory that you are about to create (which does not exist yet), use -m instead of -f or -e.

Application: Get the Directory of the Script Itself

This is a common “idiom” used to find the directory where the script is located, no matter where it is executed from.

#!/bin/bash

# Get the absolute path of this script and extract the directory part
SCRIPT_DIR=$(dirname "$(readlink -f "$0")")

echo "Script location: $SCRIPT_DIR"
# You can then load files like $SCRIPT_DIR/config.conf

Summary

The readlink command, especially with the -f option, saves you the trouble of manually tracing complex directory structures and symbolic links. It provides the “correct path” as recognized by the system. Along with pwd and ls, it is a fundamental tool for path resolution in robust shell scripts.