fix(cli): exit when the command dies from SIGPIPE

cli.js

@@ -286,7 +286,9 @@ function run (argv) {
     } else {
       // Keep the event loop alive until the re-raised signal terminates us.
       // Otherwise Node can finish normally before delivery and report exit 0.
-      setInterval(() => {}, 1000)
+      // Node ignores some signals (SIGPIPE), so fall back to the shell's
+      // 128 + signal number status instead of waiting forever.
+      setTimeout(() => process.exit(128 + os.constants.signals[signal]), 1000)
       process.kill(process.pid, signal)
     }
   })

tests/test-cli-signals.js

@@ -75,6 +75,19 @@ t.test('POSIX signal forwarding', { skip: process.platform === 'win32' }, async
     st.same(await command.exited, { code: null, signal: 'SIGTERM' })
   })
 
+  await ct.test('exits when the command dies from a signal Node ignores', async st => {
+    // Node ignores SIGPIPE, so re-raising it does not stop dotenv (`dotenv run -- cmd | head`).
+    const result = cp.spawnSync(process.execPath, ['dist/index.cjs', 'run', '-q', '--', 'sh', '-c', 'kill -PIPE $$'], {
+      cwd: path.resolve(__dirname, '..'),
+      encoding: 'utf8',
+      timeout: 5000,
+      env: { ...process.env, NODE_OPTIONS: '' }
+    })
+    st.equal(result.error, undefined)
+    st.equal(result.signal, null)
+    st.equal(result.status, 128 + os.constants.signals.SIGPIPE)
+  })
+
   await ct.test('forwards termination to subprocesses too', async st => {
     const grandchild = "process.once('SIGTERM', () => { console.log('grandchild stopped'); process.exit(0) }); setInterval(() => {}, 1000); process.send('ready')"
     const command = await launch(st, `