readlink

Overview

The readlink command displays the target of symbolic links. It resolves symbolic links and shows where they point, essential for understanding link structures and debugging link issues.

Syntax

readlink [options] file...

Common Options

Option	Description
`-f`	Follow all symbolic links
`-e`	All components must exist
`-m`	No components need exist
`-n`	Don’t output trailing newline
`-q`	Suppress error messages
`-s`	Suppress non-error messages
`-v`	Verbose output
`-z`	End output with null character

Key Use Cases

Display symbolic link targets
Resolve link chains
Debug broken links
Script path resolution
Link validation

Examples with Explanations

Example 1: Basic Usage

readlink symlink

Shows where the symbolic link points

Example 2: Follow All Links

readlink -f symlink

Resolves all symbolic links in the path

Example 3: Canonical Path

readlink -e /usr/bin/python

Shows canonical path, fails if target doesn’t exist

Example 4: Multiple Files

readlink -f link1 link2 link3

Resolves multiple symbolic links

Link Resolution

Single level:
```
readlink symlink
```
Full resolution:
```
readlink -f symlink
```
Existing files only:
```
readlink -e symlink
```

Common Usage Patterns

Check if file is a link:

if readlink "$file" >/dev/null 2>&1; then
    echo "$file is a symbolic link"
fi

Get script directory:

SCRIPT_DIR=$(dirname "$(readlink -f "$0")")

Resolve configuration files:

CONFIG_FILE=$(readlink -f ~/.config/app.conf)

Script Applications

Portable script paths:

#!/bin/bash
SCRIPT_PATH=$(readlink -f "$0")
SCRIPT_DIR=$(dirname "$SCRIPT_PATH")
cd "$SCRIPT_DIR"

Link validation:

validate_link() {
    local link="$1"
    if ! readlink -e "$link" >/dev/null 2>&1; then
        echo "Broken link: $link"
        return 1
    fi
}

Performance Analysis

Fast operation
No file content reading
Minimal system resources
Good for path resolution
Efficient link checking

Best Practices

Use -f for complete resolution
Check if target exists with -e
Handle broken links gracefully
Use in scripts for portability
Combine with other path tools

Error Handling

Broken links:

if ! readlink -e "$link" >/dev/null 2>&1; then
    echo "Link is broken or doesn't exist"
fi

Not a symbolic link:

target=$(readlink "$file" 2>/dev/null) || {
    echo "$file is not a symbolic link"
}

Integration Examples

Find broken links:

find /path -type l | while read link; do
    if ! readlink -e "$link" >/dev/null 2>&1; then
        echo "Broken: $link"
    fi
done

Link maintenance:

for link in *.link; do
    target=$(readlink "$link")
    echo "$link -> $target"
done

Advanced Usage

Quiet operation:
```
readlink -q symlink
```
No trailing newline:
```
readlink -n symlink
```
Null-terminated output:
```
readlink -z symlink
```

Troubleshooting

Permission denied errors
Broken symbolic links
Circular link references
Non-existent targets
Cross-filesystem links

Security Considerations

Validate link targets
Check for directory traversal
Verify link ownership
Monitor link changes
Handle untrusted links carefully

Alternative Methods

Using ls:
```
ls -l symlink | awk '{print $NF}'
```
Using stat:
```
stat -c %N symlink
```
Using file:
```
file symlink
```

Real-world Examples

System administration:

# Check system links
readlink /usr/bin/java
readlink /etc/alternatives/editor

Development workflow:

# Resolve project paths
PROJECT_ROOT=$(readlink -f "$(dirname "$0")/..")

Configuration management:

# Verify config links
for config in /etc/*.conf; do
    if [ -L "$config" ]; then
        echo "$config -> $(readlink "$config")"
    fi
done