How to Use Apache RewriteCond for Conditional Rewriting

RewriteCond adds conditions to RewriteRule, enabling complex URL routing logic. They are essential for CMS and framework URL handling. This guide walks through the specific troubleshooting steps to diagnose and resolve RewriteCond issues.

Before You Begin

Before you begin, be sure to have the following in place:

• A Linux server with the relevant software installed
• Access to the command line interface
• Appropriate permissions (root or sudo)

Quick Fix

Wrong

RewriteRule without any condition (applies to all requests)

Wrong: No conditions on rewrite rule

Right

RewriteCond %{REQUEST_URI} !^/(images|css|js)/ [NC]\nRewriteCond %{REQUEST_FILENAME} !-f\nRewriteCond %{REQUEST_FILENAME} !-d\nRewriteRule ^(.*)$ index.php [L]

Right: Conditions to skip existing files and static assets

Output

RewriteCond configured:\n  Skip: /images/, /css/, /js/ paths\n  Skip: existing files and directories\n  Fallback: route to index.php

Prevention

To avoid future issues, follow these best practices:

• Place RewriteCond before each RewriteRule
• Conditions use AND logic by default (OR with [OR] flag)
• Use %{REQUEST_FILENAME} for filesystem checks
• Use -f, -d, -s, -l for file existence checks
• Use [NC] for case-insensitive pattern matching

DodaTech Tools

For further assistance with any of the above issues, consider using DodaTech consulting services or DodaTech tutorials for more in-depth guidance.

Common Mistakes with mod rewrite cond

1. Misunderstanding that String is [Char] with poor performance for large text operations
2. Using foldl instead of foldl' causing stack overflow on large lists
3. Forgetting deriving (Show, Eq) on custom data types needed for debugging

These mistakes appear frequently in real-world APACHE code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ