diff --git a/lib/_launch.php b/lib/_launch.php
index b59b5f3..693b89b 100755
--- a/lib/_launch.php
+++ b/lib/_launch.php
@@ -3,7 +3,7 @@
 $internalUse = $argv[1] ?? null;
 if ($internalUse !== "--internal-use") exit("Wrong args");
 $paramsfile = $argv[2] ?? null;
-if (!file_exists($paramsfile)) exit("bad params file");
+if (!file_exists($paramsfile)) exit("Bad params file");
 $argc -= 2;
 $argv = array_merge(
   array_slice($argv, 0, 1),
@@ -14,12 +14,14 @@ $app_params = unserialize(file_get_contents($paramsfile));
 require $app_params["vendor"]["autoload"];
 
 use nur\cli\Application;
+use nur\sery\output\msg;
 use nur\sery\wip\app\app;
 use nur\sery\app\launcher;
 use nur\yaml;
 
 class _LaunchApp extends Application {
   const NAME = "_launch";
+  const USE_LOGFILE = true;
 
   const ACTION_INFOS = 0, ACTION_START = 1, ACTION_STOP = 2;
 
@@ -46,15 +48,18 @@ class _LaunchApp extends Application {
   function main() {
     $appClass = $this->args[0] ?? null;
     if ($appClass === null) {
-      self::die("Vous devez spécifier la classe de l'application");
+      msg::error("Vous devez spécifier la classe de l'application");
+      self::die();
     } elseif (!class_exists($appClass)) {
-      self::die("$appClass: Cette classe n'existe pas");
+      msg::error("$appClass: Cette classe n'existe pas");
+      self::die();
     }
     $args = array_slice($this->args, 1);
 
     $useRunfile = constant("$appClass::USE_RUNFILE");
     if (!$useRunfile) {
-      self::die("Cette application ne supporte pas l'usage de runfile");
+      msg::error("Cette application ne supporte pas l'usage de runfile");
+      self::die();
     }
 
     $runfile = app::with($appClass, self::$internal_use_app_params)->getRunfile();
diff --git a/nur_src/cli/Application.php b/nur_src/cli/Application.php
index 99e212c..7638eaa 100644
--- a/nur_src/cli/Application.php
+++ b/nur_src/cli/Application.php
@@ -9,6 +9,9 @@ use nur\config\ArrayConfig;
 use nur\msg;
 use nur\os;
 use nur\path;
+use nur\sery\app\launcher;
+use nur\sery\app\RunFile;
+use nur\sery\cl;
 use nur\sery\wip\app\app;
 use nur\sery\output\log as nlog;
 use nur\sery\output\msg as nmsg;
@@ -365,4 +368,15 @@ abstract class Application {
   }
 
   abstract function main();
+
+  const BGLAUNCH_SCRIPT = null;
+  static function runfile(): RunFile {
+    $callerParams = app::get()->getParams();
+    return app::with(static::class, $callerParams)->getRunfile();
+  }
+  static function bglaunch(?array $args=null) {
+    launcher::launch(static::class, cl::merge([
+      static::BGLAUNCH_SCRIPT,
+    ], $args));
+  }
 }
diff --git a/src/app/RunFile.php b/src/app/RunFile.php
index 0e9fdc1..0a3f20c 100644
--- a/src/app/RunFile.php
+++ b/src/app/RunFile.php
@@ -37,12 +37,13 @@ class RunFile {
   }
 
   protected function initData(bool $withDateStart=true): array {
+    $pid = $withDateStart? posix_getpid(): null;
     $dateStart = $withDateStart? new DateTime(): null;
     return [
       "name" => $this->name,
       "id" => bin2hex(random_bytes(16)),
       "pg_pid" => null,
-      "pid" => posix_getpid(),
+      "pid" => $pid,
       "serial" => 0,
       # lock
       "locked" => false,
@@ -52,6 +53,7 @@ class RunFile {
       "date_start" => $dateStart,
       "date_stop" => null,
       "exitcode" => null,
+      "is_done" => null,
       # action
       "action" => null,
       "action_date_start" => null,
@@ -72,22 +74,27 @@ class RunFile {
     $file->lockWrite();
     $data = $file->unserialize(null, false, true);
     if (!is_array($data)) {
-      $data = $this->initData();
+      $data = $this->initData(false);
       $file->ftruncate();
       $file->serialize($data, false, true);
     }
-    $file->ftruncate();
     return [$file, $data];
   }
 
   protected function serialize(SharedFile $file, array $data, ?array $merge=null): void {
+    $file->ftruncate();
     $file->serialize(self::merge($data, $merge), true, true);
   }
 
   protected function update(callable $func): void {
+    /** @var SharedFile$file */
     [$file, $data] = $this->willWrite();
     $merge = call_user_func($func, $data);
-    $this->serialize($file, $data, $merge);
+    if ($merge !== null && $merge !== false) {
+      $this->serialize($file, $data, $merge);
+    } else {
+      $file->cancelWrite();
+    }
   }
 
   function haveWorked(int $serial, ?int &$currentSerial=null): bool {
@@ -154,20 +161,20 @@ class RunFile {
     });
   }
 
-  /** tester si l'application a déjà été démarrée */
+  /** tester si l'application a déjà été démarrée au moins une fois */
   function wasStarted(): bool {
     $data = $this->read();
     return $data["date_start"] !== null;
   }
 
   /** tester si l'application est démarrée et non arrêtée */
-  function isStarted(): bool {
+  function isStarted(?array &$data=null): bool {
     $data = $this->read();
     return $data["date_start"] !== null && $data["date_stop"] === null;
   }
 
   /**
-   * vérifier si la tâche tourne et est accessible
+   * vérifier si l'application marquée comme démarrée tourne réellement
    */
   function isRunning(?array &$data=null): bool {
     $data = $this->read();
@@ -198,14 +205,14 @@ class RunFile {
     });
   }
 
-  /** tester si l'application est déjà été stoppée */
+  /** tester si l'application est déjà été stoppée au moins une fois */
   function wasStopped(): bool {
     $data = $this->read();
     return $data["date_stop"] !== null;
   }
 
   /** tester si l'application a été démarrée puis arrêtée */
-  function isStopped(): bool {
+  function isStopped(?array &$data=null): bool {
     $data = $this->read();
     return $data["date_start"] !== null && $data["date_stop"] !== null;
   }
@@ -221,6 +228,24 @@ class RunFile {
     });
   }
 
+  /**
+   * comme {@link self::isStopped()} mais ne renvoie true qu'une seule fois si
+   * $updateDone==true
+   */
+  function isDone(?array &$data=null, bool $updateDone=true): bool {
+    $done = false;
+    $this->update(function (array $ldata) use (&$done, &$data, $updateDone) {
+      $data = $ldata;
+      if ($data["date_start"] === null || $data["date_stop"] === null || $data["is_done"]) {
+        return false;
+      }
+      $done = true;
+      if (!$updateDone) return null;
+      return ["is_done" => $done];
+    });
+    return $done;
+  }
+
   #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   # gestion des actions
 
diff --git a/src/app/launcher.php b/src/app/launcher.php
index 73066d5..87834d4 100644
--- a/src/app/launcher.php
+++ b/src/app/launcher.php
@@ -8,7 +8,7 @@ use nur\sery\StateException;
 use nur\sery\wip\app\app;
 
 class launcher {
-  static function launch(string $appClass, ...$args): int {
+  static function launch(string $appClass, array $args): int {
     $app = app::get();
     $vendorBindir = $app->getVendorbindir();
     $launch_php = "$vendorBindir/_launch.php";
@@ -21,17 +21,20 @@ class launcher {
     $cmd = new Cmd([
       $launch_php,
       "--internal-use", $tmpfile->getFile(),
-      $appClass, ...$args,
+      $appClass, "--", ...$args,
     ]);
     $cmd->addRedir("null");
     $cmd->passthru($exitcode);
 
+    # attendre un peu que la commande aie le temps de s'initialiser
+    sleep(1);
+
     $tmpfile->close();
     return $exitcode;
   }
 
   static function _start(array $args, Runfile $runfile): bool {
-    if ($runfile->isLocked()) return false;
+    if ($runfile->warnIfLocked()) return false;
     $pid = pcntl_fork();
     if ($pid == -1) {
       # parent, impossible de forker
@@ -43,6 +46,7 @@ class launcher {
       ## child, fork ok
       # Créer un groupe de process, pour pouvoir les tuer toutes en même temps
       $runfile->tm_startPg();
+      $pid = posix_getpid();
       $exitcode = -776;
       try {
         # puis lancer la commande
@@ -50,7 +54,9 @@ class launcher {
         #XXX fichier de log?
         $cmd->addSource("/g/init.env");
         $cmd->addRedir("null");
+        msg::debug("$pid: launching\n".$cmd->getCmd());
         $cmd->fork_exec($exitcode);
+        msg::debug("$pid: exitcode=$exitcode");
         return true;
       } finally {
         $runfile->wfStopped($exitcode);
diff --git a/src/file/Stream.php b/src/file/Stream.php
index f28ae0a..c601623 100644
--- a/src/file/Stream.php
+++ b/src/file/Stream.php
@@ -455,4 +455,12 @@ class Stream extends AbstractIterator implements IReader, IWriter {
   function serialize($object, bool $close=true, bool $alreadyLocked=false): void {
     $this->putContents(serialize($object), $close, $alreadyLocked);
   }
+
+  /**
+   * annuler une tentative d'écriture commencée avec {@link self::canWrite()}
+   */
+  function cancelWrite(bool $close=true): void {
+    if ($this->useLocking) $this->unlock($close);
+    elseif ($close) $this->close();
+  }
 }