Add configFileMode option (#158)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

readme.md

@@ -269,6 +269,17 @@ Default: `false`
 
 Watch for any changes in the config file and call the callback for `onDidChange` or `onDidAnyChange` if set. This is useful if there are multiple processes changing the same config file.
 
+#### configFileMode
+
+Type: `number`\
+Default: `0o666`
+
+The [mode](https://en.wikipedia.org/wiki/File-system_permissions#Numeric_notation) that will be used for the config file.
+
+You would usually not need this, but it could be useful if you want to restrict the permissions of the config file. Setting a permission such as `0o600` would result in a config file that can only be accessed by the user running the program.
+
+Note that setting restrictive permissions can cause problems if different users need to read the file. A common problem is a user running your tool with and without `sudo` and then not being able to access the config the second time.
+
 ### Instance
 
 You can use [dot-notation](https://github.com/sindresorhus/dot-prop) in a `key` to access nested properties.

source/index.ts

@@ -67,6 +67,7 @@ class Conf<T extends Record<string, any> = Record<string, unknown>> implements I
 			projectSuffix: 'nodejs',
 			clearInvalidConfig: false,
 			accessPropertiesByDotNotation: true,
+			configFileMode: 0o666,
 			...partialOptions
 		};
 
@@ -461,16 +462,16 @@ class Conf<T extends Record<string, any> = Record<string, unknown>> implements I
 		// Temporary workaround for Conf being packaged in a Ubuntu Snap app.
 		// See https://github.com/sindresorhus/conf/pull/82
 		if (process.env.SNAP) {
-			fs.writeFileSync(this.path, data);
+			fs.writeFileSync(this.path, data, {mode: this.#options.configFileMode});
 		} else {
 			try {
-				atomically.writeFileSync(this.path, data);
+				atomically.writeFileSync(this.path, data, {mode: this.#options.configFileMode});
 			} catch (error: any) {
 				// Fix for https://github.com/sindresorhus/electron-store/issues/106
 				// Sometimes on Windows, we will get an EXDEV error when atomic writing
 				// (even though to the same directory), so we fall back to non atomic write
 				if (error?.code === 'EXDEV') {
-					fs.writeFileSync(this.path, data);
+					fs.writeFileSync(this.path, data, {mode: this.#options.configFileMode});
 					return;
 				}
 

source/types.ts

@@ -212,6 +212,17 @@ export interface Options<T> {
 	@default false
 	*/
 	readonly watch?: boolean;
+
+	/**
+	The [mode](https://en.wikipedia.org/wiki/File-system_permissions#Numeric_notation) that will be used for the config file.
+
+	You would usually not need this, but it could be useful if you want to restrict the permissions of the config file. Setting a permission such as `0o600` would result in a config file that can only be accessed by the user running the program.
+
+	Note that setting restrictive permissions can cause problems if different users need to read the file. A common problem is a user running your tool with and without `sudo` and then not being able to access the config the second time.
+
+	@default 0o666
+	*/
+	readonly configFileMode: number;
 }
 
 export type Migrations<T> = Record<string, (store: Conf<T>) => void>;

test/index.test-d.ts

@@ -26,6 +26,7 @@ new Conf<UnicornFoo>({encryptionKey: Buffer.from('')});
 new Conf<UnicornFoo>({encryptionKey: new Uint8Array([1])});
 new Conf<UnicornFoo>({encryptionKey: new DataView(new ArrayBuffer(2))});
 new Conf<UnicornFoo>({fileExtension: '.foo'});
+new Conf<UnicornFoo>({configFileMode: 0o600});
 new Conf<UnicornFoo>({clearInvalidConfig: false});
 new Conf<UnicornFoo>({serialize: () => 'foo'});
 new Conf<UnicornFoo>({deserialize: () => ({foo: 'foo', unicorn: true})});