### Complete Workflow Example

Source: https://context7.com/unjs/rc9/llms.txt

Demonstrates a comprehensive usage pattern for managing project and user configurations in a CLI application.

```APIDOC
## Complete Workflow Example

### Description
A comprehensive example showing typical usage patterns for a CLI application, integrating project and user configuration management.

### Code Example
```typescript
import {
  read,
  write,
  update,
  readUserConfig,
  writeUserConfig,
  updateUserConfig,
  parse,
  serialize
} from "rc9";

// Initialize default project configuration
const projectDefaults = {
  project: {
    name: "my-app",
    version: "1.0.0"
  },
  build: {
    outDir: "dist",
    minify: true,
    sourceMaps: false
  },
  server: {
    port: 3000,
    host: "localhost"
  }
};
write(projectDefaults, { name: ".myapprc" });

// Read and modify project config
const config = read({ name: ".myapprc" });
config.server.port = 8080;
write(config, { name: ".myapprc" });

// Or use update for partial changes
update({
  "build.sourceMaps": true,
  "server.cors": true
}, { name: ".myapprc" });

// Store user-specific settings (API tokens, preferences)
writeUserConfig({
  apiToken: "user-secret-token",
  defaultProject: "/path/to/project"
}, ".myapprc");

// Update user config while preserving existing values
updateUserConfig({
  lastUsed: new Date().toISOString()
}, ".myapprc");

// Parse configuration from environment or string source
const envConfig = parse(process.env.MY_APP_CONFIG || "");

// Serialize for logging or debugging
const configStr = serialize(read({ name: ".myapprc" }));
console.log("Current configuration:\n" + configStr);
```
```

--------------------------------

### Define Configuration File

Source: https://github.com/unjs/rc9/blob/main/README.md

Example content for a .conf file.

```ini
db.username=username
db.password=multi word password
db.enabled=true
```

--------------------------------

### Install RC9

Source: https://github.com/unjs/rc9/blob/main/README.md

Commands to install the package using various package managers.

```sh
# ✨ Auto-detect
npx nypm install rc9

# npm
npm install rc9

# yarn
yarn add rc9

# pnpm
pnpm add rc9

# bun
bun install rc9

# deno
deno install npm:rc9
```

--------------------------------

### Implement complete workflow

Source: https://context7.com/unjs/rc9/llms.txt

Demonstrates a full lifecycle for managing project-local and user-specific configuration files.

```typescript
import {
  read,
  write,
  update,
  readUserConfig,
  writeUserConfig,
  updateUserConfig,
  parse,
  serialize
} from "rc9";

// Initialize default project configuration
const projectDefaults = {
  project: {
    name: "my-app",
    version: "1.0.0"
  },
  build: {
    outDir: "dist",
    minify: true,
    sourceMaps: false
  },
  server: {
    port: 3000,
    host: "localhost"
  }
};
write(projectDefaults, ".myapprc");

// Read and modify project config
const config = read(".myapprc");
config.server.port = 8080;
write(config, ".myapprc");

// Or use update for partial changes
update({
  "build.sourceMaps": true,
  "server.cors": true
}, ".myapprc");

// Store user-specific settings (API tokens, preferences)
writeUserConfig({
  apiToken: "user-secret-token",
  defaultProject: "/path/to/project"
}, ".myapprc");

// Update user config while preserving existing values
updateUserConfig({
  lastUsed: new Date().toISOString()
}, ".myapprc");

// Parse configuration from environment or string source
const envConfig = parse(process.env.MY_APP_CONFIG || "");

// Serialize for logging or debugging
const configStr = serialize(read(".myapprc"));
console.log("Current configuration:\n" + configStr);
```

--------------------------------

### read

Source: https://context7.com/unjs/rc9/llms.txt

Reads a configuration file from the current working directory or a specified location.

```APIDOC
## read

### Description
Reads a configuration file from the current working directory or a specified location. This is the primary function for reading project-level configuration.

### Parameters
#### Request Body
- **options** (string|object) - Optional - The filename or an object containing { name, dir, flat }.

### Response
#### Success Response (200)
- **config** (object) - The configuration object.
```

--------------------------------

### Read and Write Configuration

Source: https://github.com/unjs/rc9/blob/main/README.md

Reading a configuration file, modifying it, and writing the changes back.

```ts
const config = read(); // or read('.conf')

// config = {
//   db: {
//     username: 'username',
//     password: 'multi word password',
//     enabled: true
//   }
// }

config.enabled = false;
write(config); // or write(config, '.conf')
```

--------------------------------

### parseFile

Source: https://context7.com/unjs/rc9/llms.txt

Reads and parses a configuration file from a specified path.

```APIDOC
## parseFile

### Description
Reads and parses a configuration file from a specified path. Returns an empty object if the file does not exist.

### Parameters
#### Path Parameters
- **path** (string) - Required - The file system path to the configuration file.

#### Query Parameters
- **options** (object) - Optional - Configuration options (e.g., { flat: boolean }).

### Response
#### Success Response (200)
- **config** (object) - The parsed configuration object or {} if file does not exist.
```

--------------------------------

### write

Source: https://context7.com/unjs/rc9/llms.txt

Writes a configuration object to a file, automatically serializing nested objects using dot notation.

```APIDOC
## write

### Description
Writes a configuration object to a file, automatically serializing nested objects using dot notation.

### Parameters
#### Request Body
- **config** (object) - Required - The configuration object to write.
- **options** (string|object) - Optional - The filename or an object containing { name, dir }.

### Response
#### Success Response (200)
- **void** - Writes the file to the disk.
```

--------------------------------

### Manage User Configuration

Source: https://github.com/unjs/rc9/blob/main/README.md

Storing and reading configuration files in the user's config directory using XDG conventions.

```js
writeUserConfig({ token: 123 }, ".zoorc"); // Will be saved in ~/.config/.zoorc

const conf = readUserConfig(".zoorc"); // { token: 123 }
```

--------------------------------

### serialize

Source: https://context7.com/unjs/rc9/llms.txt

Converts a configuration object to a string in the RC file format.

```APIDOC
## serialize

### Description
Converts a configuration object to a string in the RC file format.

### Parameters
#### Request Body
- **config** (object) - Required - The configuration object to serialize.

### Response
#### Success Response (200)
- **string** (string) - The serialized RC format string.
```

--------------------------------

### Project-Local Configuration Functions

Source: https://context7.com/unjs/rc9/llms.txt

Functions for managing configuration files within the project directory.

```APIDOC
## Project-Local Configuration Functions

### Description
Functions for reading, writing, and updating configuration files located within the project directory.

### Functions
- **`read(options?: RCOptions): object`**: Reads a configuration file.
- **`write(config: object, options?: RCOptions): void`**: Writes a configuration object to a file.
- **`update(updates: object, options?: RCOptions): object`**: Updates a configuration file by merging new values.

### Endpoint
N/A (Local file system operation)

### Parameters
- **`options`** (`RCOptions`) - Optional - Configuration options including `name`, `dir`, and `flat`.
- **`config`** (`object`) - Required for `write` - The configuration object to write.
- **`updates`** (`object`) - Required for `update` - An object containing the key-value pairs to update. Nested keys can be specified using dot notation.

### Request Example
```typescript
import { read, write, update } from "rc9";

// Initialize default project configuration
const projectDefaults = {
  project: {
    name: "my-app",
    version: "1.0.0"
  },
  build: {
    outDir: "dist",
    minify: true,
    sourceMaps: false
  },
  server: {
    port: 3000,
    host: "localhost"
  }
};
write(projectDefaults, { name: ".myapprc" });

// Read and modify project config
const config = read({ name: ".myapprc" });
config.server.port = 8080;
write(config, { name: ".myapprc" });

// Or use update for partial changes
update({
  "build.sourceMaps": true,
  "server.cors": true
}, { name: ".myapprc" });
```

### Response
- **`read`**: Returns the parsed configuration object.
- **`write`**: Returns void.
- **`update`**: Returns the entire merged configuration object.
```

--------------------------------

### Parsing and Serialization

Source: https://context7.com/unjs/rc9/llms.txt

Functions for parsing configuration from strings or environment variables and serializing configuration objects.

```APIDOC
## Parsing and Serialization

### Description
Functions for parsing configuration from various sources and serializing configuration objects into strings.

### Functions
- **`parse(source: string, options?: RCOptions): object`**: Parses configuration from a string (e.g., environment variables).
- **`serialize(config: object, options?: RCOptions): string`**: Serializes a configuration object into a string.

### Endpoint
N/A (Utility functions)

### Parameters
- **`source`** (`string`) - Required for `parse` - The string source to parse (e.g., `process.env.MY_APP_CONFIG`).
- **`config`** (`object`) - Required for `serialize` - The configuration object to serialize.
- **`options`** (`RCOptions`) - Optional - Configuration options.

### Request Example
```typescript
import { read, serialize, parse } from "rc9";

// Parse configuration from environment or string source
const envConfig = parse(process.env.MY_APP_CONFIG || "");

// Serialize for logging or debugging
const configStr = serialize(read(".myapprc"));
console.log("Current configuration:\n" + configStr);
```

### Response
- **`parse`**: Returns the parsed configuration object.
- **`serialize`**: Returns the serialized configuration as a string.
```

--------------------------------

### update

Source: https://context7.com/unjs/rc9/llms.txt

Reads an existing configuration file, merges it with new values, and writes the result back.

```APIDOC
## update

### Description
Reads an existing configuration file, merges it with new values, and writes the result back. New values take precedence over existing ones.

### Parameters
#### Request Body
- **updates** (object) - Required - The new values to merge.
- **filename** (string) - Optional - The name of the file to update.

### Response
#### Success Response (200)
- **config** (object) - The merged configuration object.
```

--------------------------------

### Import RC9 Utilities

Source: https://github.com/unjs/rc9/blob/main/README.md

Importing the available utility functions for ESM environments.

```js
import {
  defaults,
  parse,
  parseFile,
  read,
  readUser,
  serialize,
  write,
  writeUser,
  readUserConfig,
  writeUserConfig,
  updateUserConfig,
  update,
  updateUser,
} from "rc9";
```

--------------------------------

### Read user configuration

Source: https://context7.com/unjs/rc9/llms.txt

Reads a configuration file from the user's XDG-compliant config directory.

```typescript
import { readUserConfig } from "rc9";

// Read from ~/.config/.myapprc
const userConfig = readUserConfig(".myapprc");

// Example: Reading user preferences for a CLI tool
// File: ~/.config/.mytoolrc
// theme=dark
// editor=vim
// notifications=true
const prefs = readUserConfig(".mytoolrc");
console.log(prefs.theme);        // "dark"
console.log(prefs.editor);       // "vim"
console.log(prefs.notifications); // true
```

--------------------------------

### Write user configuration

Source: https://context7.com/unjs/rc9/llms.txt

Writes a configuration object to the user's XDG-compliant config directory.

```typescript
import { writeUserConfig, readUserConfig } from "rc9";

// Store user preferences
writeUserConfig({
  token: "abc123xyz",
  defaultOrg: "my-organization",
  preferences: {
    theme: "dark",
    notifications: true
  }
}, ".myapprc");
// Creates ~/.config/.myapprc

// Verify the write
const config = readUserConfig(".myapprc");
console.log(config.token); // "abc123xyz"
```

--------------------------------

### Write configuration files with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Writes a configuration object to a file, automatically serializing nested objects using dot notation.

```typescript
import { write, read } from "rc9";

// Write configuration to default .conf file
const config = {
  db: {
    host: "localhost",
    port: 5432,
    credentials: {
      username: "admin",
      password: "secret"
    }
  },
  cache: {
    enabled: true,
    ttl: 3600
  }
};

write(config);
// Creates .conf file:
// db.host="localhost"
// db.port=5432
// db.credentials.username="admin"
// db.credentials.password="secret"
// cache.enabled=true
// cache.ttl=3600

// Write to a named file
write(config, ".myapprc");

// Write with options
write(config, {
  name: ".myapprc",
  dir: "/path/to/project"
});
```

--------------------------------

### Parse configuration files with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Reads and parses a configuration file from a specified path. Returns an empty object if the file does not exist.

```typescript
import { parseFile } from "rc9";

// Parse a specific configuration file
const config = parseFile("/path/to/.myapprc");
// Result: parsed configuration object or {} if file doesn't exist

// With options
const flatConfig = parseFile("/path/to/.myapprc", { flat: true });
```

--------------------------------

### Read configuration files with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Reads a configuration file from the current working directory or a specified location. This is the primary function for reading project-level configuration.

```typescript
import { read } from "rc9";

// Read default .conf file from current directory
const config = read();

// Read a named configuration file
const npmConfig = read(".npmrc");

// Read with full options
const customConfig = read({
  name: ".myapprc",
  dir: "/path/to/project",
  flat: false
});

// Example: Reading database configuration
// File: .conf
// db.host=localhost
// db.port=5432
// db.ssl=true
const dbConfig = read();
console.log(dbConfig.db.host); // "localhost"
console.log(dbConfig.db.port); // 5432 (number, not string)
console.log(dbConfig.db.ssl);  // true (boolean)
```

--------------------------------

### writeUserConfig

Source: https://context7.com/unjs/rc9/llms.txt

Writes a configuration object to the user's config directory, supporting XDG conventions.

```APIDOC
## writeUserConfig

### Description
Writes a configuration object to the user's config directory (`$XDG_CONFIG_HOME` or `~/.config`).

### Method
`writeUserConfig(config: object, fileName: string): void`

### Endpoint
N/A (Local file system operation)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **config** (object) - Required - The configuration object to write.
- **fileName** (string) - Required - The name of the configuration file.

### Request Example
```typescript
import { writeUserConfig, readUserConfig } from "rc9";

// Store user preferences
writeUserConfig({
  token: "abc123xyz",
  defaultOrg: "my-organization",
  preferences: {
    theme: "dark",
    notifications: true
  }
}, ".myapprc");
// Creates ~/.config/.myapprc

// Verify the write
const config = readUserConfig(".myapprc");
console.log(config.token); // "abc123xyz"
```

### Response
#### Success Response (200)
None (operation is void).
```

--------------------------------

### parse

Source: https://context7.com/unjs/rc9/llms.txt

Parses a configuration string into a JavaScript object with support for dot notation and automatic type conversion.

```APIDOC
## parse

### Description
Parses a configuration string into a JavaScript object. Supports dot notation for nested objects, array syntax with `[]`, and automatic type conversion.

### Parameters
#### Request Body
- **input** (string) - Required - The configuration string to parse.
- **options** (object) - Optional - Configuration options (e.g., { flat: boolean }).

### Request Example
parse("db.port=5432\ndb.enabled=true")

### Response
#### Success Response (200)
- **object** (object) - The parsed configuration object.
```

--------------------------------

### Serialize configuration objects with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Converts a configuration object to a string in the RC file format.

```typescript
import { serialize } from "rc9";

const config = {
  api: {
    url: "https://api.example.com",
    timeout: 5000,
    retry: true
  },
  logging: {
    level: "info"
  }
};

const serialized = serialize(config);
// Output:
// api.url="https://api.example.com"
// api.timeout=5000
// api.retry=true
// logging.level="info"
```

--------------------------------

### Configure RCOptions

Source: https://context7.com/unjs/rc9/llms.txt

Defines configuration options for rc9 functions, including file name, directory path, and object flattening behavior.

```typescript
import { read, write, update } from "rc9";

interface RCOptions {
  name?: string;  // Config file name (default: ".conf")
  dir?: string;   // Directory path (default: process.cwd())
  flat?: boolean; // Disable object flattening (default: false)
}

// Using options with different functions
const config = read({
  name: ".myapprc",
  dir: "/custom/path",
  flat: false
});

write({ key: "value" }, {
  name: ".myapprc",
  dir: "/custom/path"
});

update({ newKey: "newValue" }, {
  name: ".myapprc",
  dir: "/custom/path",
  flat: true
});
```

--------------------------------

### Update configuration files with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Reads an existing configuration file, merges it with new values, and writes the result back. New values take precedence over existing ones.

```typescript
import { update, read } from "rc9";

// Update specific values while preserving others
// Existing .conf: db.host=localhost, db.port=5432
update({ "db.port": 3306 });
// Result: db.host=localhost, db.port=3306

// Update nested values
update({
  "db.credentials.password": "newpassword",
  "cache.enabled": false
});

// Push to arrays using [] syntax
update({ "plugins[]": "newPlugin" });
// Appends "newPlugin" to existing plugins array

// Update returns the merged configuration
const newConfig = update({ debug: true }, ".myapprc");
console.log(newConfig);
```

--------------------------------

### readUserConfig

Source: https://context7.com/unjs/rc9/llms.txt

Reads a configuration file from the user's config directory, following XDG Base Directory conventions.

```APIDOC
## readUserConfig

### Description
Reads a configuration file from the user's config directory (`$XDG_CONFIG_HOME` or `~/.config`). Follows XDG Base Directory conventions.

### Method
`readUserConfig(fileName: string): object`

### Endpoint
N/A (Local file system operation)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```typescript
import { readUserConfig } from "rc9";

// Read from ~/.config/.myapprc
const userConfig = readUserConfig(".myapprc");

// Example: Reading user preferences for a CLI tool
// File: ~/.config/.mytoolrc
// theme=dark
// editor=vim
// notifications=true
const prefs = readUserConfig(".mytoolrc");
console.log(prefs.theme);        // "dark"
console.log(prefs.editor);       // "vim"
console.log(prefs.notifications); // true
```

### Response
#### Success Response (200)
- **object** - The parsed configuration object from the user's config file.
```

--------------------------------

### RCOptions Interface

Source: https://context7.com/unjs/rc9/llms.txt

Defines the configuration options available for RC9 functions.

```APIDOC
## RCOptions Interface

### Description
Configuration options for all RC9 functions (`read`, `write`, `update`, `readUserConfig`, `writeUserConfig`, `updateUserConfig`).

### Interface Definition
```typescript
interface RCOptions {
  name?: string;  // Config file name (default: ".conf")
  dir?: string;   // Directory path (default: process.cwd() for project-local, or user's config dir for user-specific)
  flat?: boolean; // Disable object flattening (default: false)
}
```

### Usage Example
```typescript
import { read, write, update } from "rc9";

// Using options with different functions
const config = read({
  name: ".myapprc",
  dir: "/custom/path",
  flat: false
});

write({ key: "value" }, {
  name: ".myapprc",
  dir: "/custom/path"
});

update({ newKey: "newValue" }, {
  name: ".myapprc",
  dir: "/custom/path",
  flat: true
});
```
```

--------------------------------

### RC9 User Configuration API

Source: https://github.com/unjs/rc9/blob/main/README.md

Functions for managing configuration files within the user's home directory, adhering to XDG conventions.

```APIDOC
## RC9 User Configuration API

### Description
Provides functions to read, write, and update configuration files stored in the user's config directory (e.g., `~/.config`). These functions follow XDG base directory specifications.

### Methods

#### `readUserConfig(options?: RCOptions | string): RC`
Reads configuration from the user's config directory.

#### `writeUserConfig(config: RC, options?: RCOptions | string): void`
Writes the given configuration object to the user's config directory.

#### `updateUserConfig(config: RC, options?: RCOptions | string): RC`
Updates an existing configuration in the user's config directory and returns the updated configuration.

### Parameters

#### `options` (RCOptions | string)
- `name` (string) - Optional - The name of the configuration file (e.g., '.zoorc').
- `dir` (string) - Optional - The directory to look for the configuration file (default: user's config directory).
- `flat` (boolean) - Optional - If true, disables automatic flattening/unflattening of nested keys (default: false).

### Examples

**Writing User Configuration:**
```ts
import { writeUserConfig } from 'rc9';

writeUserConfig({ token: 123 }, '.zoorc'); // Saved in ~/.config/.zoorc
```

**Reading User Configuration:**
```ts
import { readUserConfig } from 'rc9';

const conf = readUserConfig('.zoorc'); // Reads { token: 123 } from ~/.config/.zoorc
console.log(conf);
```

**Updating User Configuration:**
```ts
import { updateUserConfig } from 'rc9';

updateUserConfig({ 'api.key': 'new-key' }, '.apprc');
```

### Deprecated Methods

> **Note:** `readUser`, `writeUser`, and `updateUser` are deprecated. Use `readUserConfig`, `writeUserConfig`, and `updateUserConfig` instead.
```

--------------------------------

### RC9 Configuration Management API

Source: https://github.com/unjs/rc9/blob/main/README.md

This section covers the core functions for reading, writing, and updating configuration files using RC9.

```APIDOC
## RC9 Configuration Management API

### Description
Provides functions to read, write, and update configuration files.

### Methods

#### `read(options?: RCOptions | string): RC`
Reads configuration from a file. If no path is provided, it defaults to '.conf'.

#### `write(config: RC, options?: RCOptions | string): void`
Writes the given configuration object to a file. Defaults to '.conf'.

#### `update(config: RC, options?: RCOptions | string): RC`
Updates an existing configuration with new values and returns the updated configuration.

#### `parse(contents: string, options?: RCOptions): RC`
Parses configuration content from a string.

#### `parseFile(path: string, options?: RCOptions): RC`
Parses configuration directly from a file path.

#### `serialize(config: RC): string`
Serializes a configuration object into a string format.

### Parameters

#### `options` (RCOptions | string)
- `name` (string) - Optional - The name of the configuration file (default: '.conf').
- `dir` (string) - Optional - The directory to look for the configuration file (default: process.cwd()).
- `flat` (boolean) - Optional - If true, disables automatic flattening/unflattening of nested keys (default: false).

### Types

#### `RC`
- `Record<string, any>` - Represents the configuration object.

#### `RCOptions`
- `name?: string`
- `dir?: string`
- `flat?: boolean`

### Examples

**Reading Configuration:**
```ts
import { read } from 'rc9';

const config = read(); // Reads from '.conf' by default
console.log(config);

const customConfig = read('myconfig.json'); // Reads from 'myconfig.json'
```

**Writing Configuration:**
```ts
import { write } from 'rc9';

const newConfig = { db: { enabled: true } };
write(newConfig); // Writes to '.conf' by default

write(newConfig, 'myconfig.yaml'); // Writes to 'myconfig.yaml'
```

**Updating Configuration:**
```ts
import { update } from 'rc9';

// Update a nested value
update({ 'db.enabled': false });

// Push to an array
update({ 'modules[]': 'new-module' });
```
```

--------------------------------

### Parse configuration strings with RC9

Source: https://context7.com/unjs/rc9/llms.txt

Parses a configuration string into a JavaScript object. Supports dot notation, array syntax, and flat mode.

```typescript
import { parse } from "rc9";

// Basic key-value parsing
const config = parse(`
db.username=admin
db.password=secret123
db.port=5432
db.enabled=true
`);
// Result: { db: { username: "admin", password: "secret123", port: 5432, enabled: true } }

// Array syntax using []
const arrayConfig = parse(`
modules[]=auth
modules[]=logging
modules[]=cache
`);
// Result: { modules: ["auth", "logging", "cache"] }

// Flat mode (disable unflattening)
const flatConfig = parse(`x=1
x.y=2`, { flat: true });
// Result: { x: 1, "x.y": 2 }
```

--------------------------------

### Update Configuration

Source: https://github.com/unjs/rc9/blob/main/README.md

Updating specific configuration keys or pushing values to arrays.

```ts
update({ "db.enabled": false }); // or update(..., { name: '.conf' })
```

```ts
update({ "modules[]": "test" });
```

--------------------------------

### Library Exports

Source: https://github.com/unjs/rc9/blob/main/README.md

Type definitions and function signatures for the RC9 library.

```ts
const defaults: RCOptions;
function parse(contents: string, options?: RCOptions): RC;
function parseFile(path: string, options?: RCOptions): RC;
function read(options?: RCOptions | string): RC;
function readUserConfig(options?: RCOptions | string): RC;
function serialize(config: RC): string;
function write(config: RC, options?: RCOptions | string): void;
function writeUserConfig(config: RC, options?: RCOptions | string): void;
function update(config: RC, options?: RCOptions | string): RC;
function updateUserConfig(config: RC, options?: RCOptions | string): RC;
```

```ts
type RC = Record<string, any>;
interface RCOptions {
  name?: string;
  dir?: string;
  flat?: boolean;
}
```

```ini
{
  name: '.conf',
  dir: process.cwd(),
  flat: false
}
```

--------------------------------

### Update user configuration

Source: https://context7.com/unjs/rc9/llms.txt

Merges new values into an existing configuration file within the user's config directory.

```typescript
import { updateUserConfig, readUserConfig } from "rc9";

// Update user token without affecting other settings
updateUserConfig({ token: "new-token-value" }, ".myapprc");

// Update nested preferences
updateUserConfig({
  "preferences.theme": "light",
  "preferences.fontSize": 14
}, ".myapprc");

// The function returns the merged configuration
const updatedConfig = updateUserConfig({
  lastLogin: Date.now()
}, ".myapprc");
console.log(updatedConfig);
```

--------------------------------

### updateUserConfig

Source: https://context7.com/unjs/rc9/llms.txt

Updates a configuration file in the user's config directory by merging new values with existing configuration.

```APIDOC
## updateUserConfig

### Description
Updates a configuration file in the user's config directory by merging new values with existing configuration.

### Method
`updateUserConfig(updates: object, fileName: string): object`

### Endpoint
N/A (Local file system operation)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **updates** (object) - Required - An object containing the key-value pairs to update. Nested keys can be specified using dot notation (e.g., `"preferences.theme": "light"`).
- **fileName** (string) - Required - The name of the configuration file.

### Request Example
```typescript
import { updateUserConfig, readUserConfig } from "rc9";

// Update user token without affecting other settings
updateUserConfig({ token: "new-token-value" }, ".myapprc");

// Update nested preferences
updateUserConfig({
  "preferences.theme": "light",
  "preferences.fontSize": 14
}, ".myapprc");

// The function returns the merged configuration
const updatedConfig = updateUserConfig({
  lastLogin: Date.now()
}, ".myapprc");
console.log(updatedConfig);
```

### Response
#### Success Response (200)
- **object** - The entire merged configuration object after the update.
```

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