Add function to detect current shell (#8)

index.d.ts

@@ -17,3 +17,18 @@ console.log(defaultShell);
 declare const defaultShell: string;
 
 export default defaultShell;
+
+/**
+This can be useful if the default shell changes at runtime.
+
+@returns The user's current default shell.
+
+@example
+```
+import {detectDefaultShell} from 'default-shell';
+
+console.log(detectDefaultShell());
+//=> '/bin/bash'
+```
+*/
+export function detectDefaultShell(): string;

index.js

@@ -1,7 +1,7 @@
 import process from 'node:process';
 import {userInfo} from 'node:os';
 
-const defaultShell = (() => {
+export const detectDefaultShell = () => {
 	const {env} = process;
 
 	if (process.platform === 'win32') {
@@ -20,6 +20,9 @@ const defaultShell = (() => {
 	}
 
 	return env.SHELL || '/bin/sh';
-})();
+};
+
+// Stores default shell when imported.
+const defaultShell = detectDefaultShell();
 
 export default defaultShell;

index.test-d.ts

@@ -1,4 +1,5 @@
 import {expectType} from 'tsd';
-import defaultShell from './index.js';
+import defaultShell, {detectDefaultShell} from './index.js';
 
 expectType<string>(defaultShell);
+expectType<string>(detectDefaultShell());

readme.md

@@ -11,7 +11,7 @@ npm install default-shell
 ## Usage
 
 ```js
-import defaultShell from 'default-shell';
+import defaultShell, {detectDefaultShell} from 'default-shell';
 
 // macOS
 console.log(defaultShell);
@@ -20,4 +20,8 @@ console.log(defaultShell);
 // Windows
 console.log(defaultShell);
 //=> 'C:\\WINDOWS\\system32\\cmd.exe'
+
+// This can be useful if the default shell changes at runtime.
+console.log(detectDefaultShell());
+//=> '/bin/bash'
 ```

test.js

@@ -1,7 +1,11 @@
 import process from 'node:process';
 import test from 'ava';
-import defaultShell from './index.js';
+import defaultShell, {detectDefaultShell} from './index.js';
 
 test('main', t => {
 	t.true(defaultShell.startsWith(process.platform === 'win32' ? 'C:\\' : '/bin/'));
 });
+
+test('detect', t => {
+	t.is(detectDefaultShell(), defaultShell);
+});