Try_files directive in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the try_files directive do in nginx?

It checks for the existence of files or directories in order, and serves the first one found. If none are found, it can redirect to a fallback URI or return an error.

beginner

How do you write a try_files directive to check for index.html and then fallback to index.php?

try_files /index.html /index.php;

beginner

What happens if none of the files in try_files exist and no fallback is specified?

nginx returns a 404 Not Found error by default.

intermediate

Why is try_files preferred over if statements for checking file existence in nginx?

try_files is more efficient and designed for this purpose, avoiding complex and error-prone if conditions.

intermediate

Give an example of a try_files directive that tries $uri, $uri/, and then redirects to /index.php with query string.

try_files $uri $uri/ /index.php?$query_string;

What does try_files $uri /fallback.html; do?

A Always serves /fallback.html

B Returns a 500 error if $uri does not exist

C Redirects to $uri

D Serves the file at $uri if it exists, otherwise serves /fallback.html

The directive tries to serve the file at $uri first. If it doesn't exist, it serves /fallback.html.

If try_files does not find any file and no fallback is given, what is the default response?

A 200 OK

B 404 Not Found

C 500 Internal Server Error

D 301 Redirect

nginx returns a 404 Not Found error by default when no file is found and no fallback is specified.

Which is a valid use of try_files?

A try_files $uri $uri/ /index.php?$args;

B try_files if ($uri) { return 404; };

C try_files $uri then /index.html;

D try_files $uri || /index.html;

Option A is the correct syntax for try_files. The others are invalid.

Why should try_files be used instead of if to check file existence?

A try_files is faster and less error-prone

B if is deprecated in nginx

C try_files can only check directories

D if cannot check files

try_files is optimized for checking files and is more efficient than if statements.

What does this directive do? try_files $uri $uri/ =404;

A Redirects to $uri/

B Always returns 404

C Tries $uri, then $uri/ and returns 404 if none found

D Serves $uri only

It tries to serve $uri, then $uri/ (directory), and returns a 404 error if neither exists.

Explain how the try_files directive works in nginx and why it is useful.

Think about how nginx decides which file to serve when multiple options exist.

Write a try_files directive that tries the requested URI, then the URI as a directory, and finally redirects to /index.php with query parameters.

Use variables $uri and $query_string in the directive.

Practice

1. What is the main purpose of the try_files directive in nginx?

easy

A. To check multiple files or paths in order and serve the first found

B. To restart the nginx server automatically

C. To define user permissions for files

D. To log errors in a custom file

Solution

1. Step 1: Understand the role of try_files

   The try_files directive checks a list of files or paths one by one.

2. Step 2: Identify its purpose

   It serves the first file found or falls back to a default if none exist.

3. Final Answer:

   To check multiple files or paths in order and serve the first found -> Option A

4. Quick Check:

   try_files = check files in order [OK]

Hint: Remember: try_files tries files one by one until success [OK]

Common Mistakes:

• Thinking try_files restarts nginx
• Confusing try_files with permission settings
• Assuming try_files logs errors

2. Which of the following is the correct syntax for the try_files directive in nginx?

easy

A. try_files file1 file2 fallback;

B. try_files file1 file2 =404;

C. try_files file1, file2, fallback;

D. try_files (file1 file2 fallback);

Solution

1. Step 1: Recall try_files syntax rules

   The try_files directive lists files separated by spaces, ending with a fallback like =404.

2. Step 2: Identify correct syntax

   try_files file1 file2 =404; uses spaces and ends with =404, which is valid syntax.

3. Final Answer:

   try_files file1 file2 =404; -> Option B

4. Quick Check:

   try_files syntax uses spaces and fallback [OK]

Hint: Use spaces, no commas or parentheses, end with fallback [OK]

Common Mistakes:

• Using commas between file names
• Adding parentheses around files
• Omitting fallback or using wrong fallback syntax

3. Given this nginx config snippet:

location / {
  try_files $uri $uri/ /index.html;
}

What happens when a user requests /about and /about is not a file but /about/ is a directory?

medium

A. nginx serves the /about file

B. nginx returns a 404 error

C. nginx serves the /about/ directory index

D. nginx serves /index.html fallback

Solution

1. Step 1: Understand try_files order

   nginx first checks if /about file exists, then /about/ directory.

2. Step 2: Apply to given request

   /about file is missing, but /about/ directory exists, so nginx serves the directory index.

3. Final Answer:

   nginx serves the /about/ directory index -> Option C

4. Quick Check:

   try_files checks files then directories [OK]

Hint: try_files checks files then directories in order [OK]

Common Mistakes:

• Assuming it serves /index.html fallback immediately
• Thinking it returns 404 if file missing
• Ignoring directory check after file check

4. Identify the error in this nginx config snippet:

location / {
  try_files $uri, $uri/, /fallback.html;
}

medium

A. Using commas between file names is invalid syntax

B. Missing semicolon at the end of try_files

C. Fallback file must be =404, not /fallback.html

D. Variables like $uri cannot be used in try_files

Solution

1. Step 1: Check try_files syntax

   try_files expects file names separated by spaces, not commas.

2. Step 2: Identify error in snippet

   The commas after $uri and $uri/ cause syntax error.

3. Final Answer:

   Using commas between file names is invalid syntax -> Option A

4. Quick Check:

   try_files uses spaces, no commas [OK]

Hint: No commas in try_files list, only spaces [OK]

Common Mistakes:

• Adding commas between file names
• Confusing fallback with error codes
• Thinking variables are disallowed in try_files

5. You want nginx to try serving /images/$uri, then /images/default.png if the first doesn't exist. Which try_files directive correctly implements this?

hard

A. try_files /images/$uri /images/default.png /index.html;

B. try_files $uri /images/default.png;

C. try_files /images/$uri /images/default.png=404;

D. try_files /images/$uri /images/default.png;

Solution

1. Step 1: Understand file paths in try_files

   To check /images/$uri first, it must be the first argument.

2. Step 2: Choose fallback file

   If the first file is missing, serve /images/default.png as fallback.

3. Step 3: Validate options

   try_files /images/$uri /images/default.png; matches this logic exactly without extra fallbacks or error codes.

4. Final Answer:

   try_files /images/$uri /images/default.png; -> Option D

5. Quick Check:

   try_files lists files in order, fallback last [OK]

Hint: List files in order, fallback last without extra codes [OK]

Common Mistakes:

• Using $uri without /images/ prefix
• Adding unnecessary fallback like =404
• Ending with unrelated fallback like /index.html