Support Android devices without 'whoami'

Not clear how many of these there are, but there's at least one Android
Studio emulator image (API 22) that doesn't include this, and it's easy
to work around.

Author: pimterry

src/interceptors/android/adb-commands.ts

@@ -170,34 +170,34 @@ export async function getRootCommand(adbClient: Adb.DeviceClient): Promise<RootC
     const rootTestScriptPath = `${ANDROID_TEMP}/htk-root-test.sh`;
 
     try {
-        // Just running 'whoami' doesn't fully check certain tricky cases around how the root commands
-        // handle multiple arguments etc. Pushing & running this script is an accurate test of which
-        // root mechanisms will actually work on this device:
+        // Just running 'id' doesn't fully check certain tricky cases around how the root commands handle
+        // multiple arguments etc. N.b. whoami also doesn't exist on older devices. Pushing & running
+        // this script is an accurate test of which root mechanisms will actually work on this device:
         let rootTestCommand = ['sh', rootTestScriptPath];
         try {
             await pushFile(adbClient, stringAsStream(`
                 set -e # Fail on error
-                whoami # Log the current user name, to confirm if we're root
+                id # Log the current user details, to confirm if we're root
             `), rootTestScriptPath, 0o444);
         } catch (e) {
             console.log(`Couldn't write root test script to ${rootTestScriptPath}`, e);
-            // Ok, so we can't write the test script, but let's still test for root via whoami directly,
+            // Ok, so we can't write the test script, but let's still test for root  directly,
             // because maybe if we get root then that won't be a problem
-            rootTestCommand = ['whoami'];
+            rootTestCommand = ['id'];
         }
 
-        // Run our whoami script with each of the possible root commands
+        // Run our root test script with each of the possible root commands
         const rootCheckResults = await Promise.all(
             runAsRootCommands.map((runAsRoot) =>
                 run(adbClient, runAsRoot(...rootTestCommand), { timeout: 1000 })
                     .catch((e: any) => console.log(e.message ?? e))
-                .then((whoami) => ({ cmd: runAsRoot, whoami }))
+                .then((result) => ({ cmd: runAsRoot, result }))
             )
         )
 
-        // Filter to just commands that successfully printed 'root'
+        // Filter to just commands that successfully printed 'uid=0(root)'
         const validRootCommands = rootCheckResults
-            .filter((result) => (result.whoami || '').trim() === 'root')
+            .filter((result) => (result.result || '').includes('uid=0(root)'))
             .map((result) => result.cmd);
 
         if (validRootCommands.length >= 1) return validRootCommands[0];
@@ -214,11 +214,11 @@ export async function getRootCommand(adbClient: Adb.DeviceClient): Promise<RootC
         // they're still here, and wait a few seconds for them to come back if not.
 
         await delay(500); // Wait, since they may not disconnect immediately
-        const whoami = await waitUntil(250, 10, (): Promise<string | false> => {
+        const idResult = await waitUntil(250, 10, (): Promise<string | false> => {
             return run(adbClient, rootTestCommand, { timeout: 1000 }).catch(() => false)
         }).catch(console.log);
 
-        return (whoami || '').trim() === 'root'
+        return (idResult || '').includes('uid=0(root)')
             ? (...cmd: string[]) => cmd // All commands now run as root
             : undefined; // Still not root, no luck.
     } catch (e) {