diff --git a/.idea/nur-sery.iml b/.idea/nur-sery.iml
index 6c8130a..35cbd28 100644
--- a/.idea/nur-sery.iml
+++ b/.idea/nur-sery.iml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <module type="WEB_MODULE" version="4">
-  <component name="NewModuleRootManager">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" packagePrefix="nur\sery\" />
       <sourceFolder url="file://$MODULE_DIR$/tests" isTestSource="true" packagePrefix="nur\sery\" />
diff --git a/bin/bg-launcher.php b/bin/bg-launcher.php
new file mode 100755
index 0000000..8d8fe0c
--- /dev/null
+++ b/bin/bg-launcher.php
@@ -0,0 +1,67 @@
+#!/usr/bin/php
+<?php
+require $_composer_autoload_path?? __DIR__.'/../vendor/autoload.php';
+
+use nur\sery\output\msg;
+use nur\sery\wip\app\app2;
+use nur\sery\wip\app\cli\Application;
+use nur\sery\wip\app\cli\bg_launcher;
+use nur\yaml;
+
+class BgLauncherApp extends Application {
+  const PROJDIR = __DIR__.'/../..';
+
+  const ACTION_INFOS = 0, ACTION_START = 1, ACTION_STOP = 2;
+  const ARGS = [
+    "purpose" => "lancer un script en tâche de fond",
+    "usage" => "ApplicationClass args...",
+
+    ["-i", "--infos", "name" => "action", "value" => self::ACTION_INFOS,
+      "help" => "Afficher des informations sur la tâche",
+    ],
+    ["-s", "--start", "name" => "action", "value" => self::ACTION_START,
+      "help" => "Démarrer la tâche",
+    ],
+    ["-k", "--stop", "name" => "action", "value" => self::ACTION_STOP,
+      "help" => "Arrêter la tâche",
+    ],
+  ];
+
+  protected int $action = self::ACTION_START;
+
+  protected ?array $args = null;
+
+  function main() {
+    $appClass = $this->args[0] ?? null;
+    if ($appClass === null) {
+      self::die("Vous devez spécifier la classe de l'application");
+    }
+    $appClass = str_replace("/", "\\", $appClass);
+    if (!class_exists($appClass)) {
+      self::die("$appClass: classe non trouvée");
+    }
+    $args = array_slice($this->args, 1);
+
+    $useRunfile = constant("$appClass::USE_RUNFILE");
+    if (!$useRunfile) {
+      self::die("Cette application ne supporte le lancement en tâche de fond");
+    }
+
+    $runfile = app2::with($appClass)->getRunfile();
+    switch ($this->action) {
+    case self::ACTION_START:
+      bg_launcher::_start($args, $runfile);
+      break;
+    case self::ACTION_STOP:
+      bg_launcher::_stop($runfile);
+      break;
+    case self::ACTION_INFOS:
+      yaml::dump($runfile->read());
+      break;
+    }
+  }
+}
+
+$params = app2::params_getenv();
+if ($params !== null) app2::init($params);
+BgLauncherApp::run();
diff --git a/composer.json b/composer.json
index b7690fd..6b029ff 100644
--- a/composer.json
+++ b/composer.json
@@ -65,6 +65,7 @@
 	},
 	"bin": [
 		"lib/_launch.php",
+		"bin/bg-launcher.php",
 		"nur_bin/compctl.php",
 		"nur_bin/compdep.php",
 		"nur_bin/cachectl.php",
diff --git a/nur_bin/steam-train.php b/nur_bin/steam-train.php
index 86e5496..dbde68a 100755
--- a/nur_bin/steam-train.php
+++ b/nur_bin/steam-train.php
@@ -2,6 +2,6 @@
 <?php
 require $_composer_autoload_path?? __DIR__.'/../vendor/autoload.php';
 
-use nur\sery\wip\tools\SteamTrainApp;
+use nur\sery\tools\SteamTrainApp;
 
 SteamTrainApp::run();
diff --git a/src/os/sh.php b/src/os/sh.php
index 129af47..f1e9891 100644
--- a/src/os/sh.php
+++ b/src/os/sh.php
@@ -2,7 +2,9 @@
 namespace nur\sery\os;
 
 use nur\sery\cl;
+use nur\sery\ExitError;
 use nur\sery\StateException;
+use nur\sery\wip\app\app2;
 
 class sh {
   static final function _quote(string $value): string {
@@ -144,12 +146,12 @@ class sh {
     $pid = pcntl_fork();
     if ($pid == -1) {
       // parent, impossible de forker
-      throw new StateException("unable to fork");
+      throw new ExitError(app2::EC_FORK_PARENT, "unable to fork");
     } elseif ($pid) {
       // parent, fork ok
       pcntl_waitpid($pid, $status);
       if (pcntl_wifexited($status)) $retcode = pcntl_wexitstatus($status);
-      else $retcode = 127;
+      else $retcode = app2::EC_FORK_CHILD;
       return $retcode == 0;
     }
     // child, fork ok
diff --git a/wip/tools/SteamTrainApp.php b/src/tools/SteamTrainApp.php
similarity index 59%
rename from wip/tools/SteamTrainApp.php
rename to src/tools/SteamTrainApp.php
index 6bf29b1..c05dc95 100644
--- a/wip/tools/SteamTrainApp.php
+++ b/src/tools/SteamTrainApp.php
@@ -1,27 +1,31 @@
 <?php
-namespace nur\sery\wip\tools;
+namespace nur\sery\tools;
 
 use nur\sery\output\msg;
 use nur\sery\wip\app\app2;
 use nur\sery\wip\app\cli\Application;
 
 class SteamTrainApp extends Application {
+  const PROJDIR = __DIR__.'/../..';
   const TITLE = "Train à vapeur";
-  const USE_SIGNAL_HANDLER = true;
   const USE_LOGFILE = true;
   const USE_RUNFILE = true;
   const USE_RUNLOCK = true;
+  const USE_SIGNAL_HANDLER = true;
 
   const ARGS = [
     "purpose" => self::TITLE,
+    "description" => <<<EOT
+Cette application peut être utilisée pour tester le lancement des tâches de fond
+EOT,
   ];
 
   function main() {
-    $runfile = app2::get()->getRunfile();
-    $runfile->action("Running train...", 100);
-    for ($i = 1; $i <= 100; $i++) {
+    $count = 100;
+    app2::action("Running train...", $count);
+    for ($i = 1; $i <= $count; $i++) {
       msg::print("Tchou-tchou! x $i");
-      $runfile->step();
+      app2::step();
       sleep(1);
     }
   }
diff --git a/tests/wip/app/argsTest.php b/tests/wip/app/argsTest.php
new file mode 100644
index 0000000..bea16f0
--- /dev/null
+++ b/tests/wip/app/argsTest.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace nur\sery\wip\app;
+
+use nulib\tests\TestCase;
+
+class argsTest extends TestCase {
+  function testFrom_array() {
+    self::assertSame([], args::from_array(null));
+    self::assertSame([], args::from_array([]));
+    self::assertSame([], args::from_array([false]));
+    self::assertSame(["x"], args::from_array(["x", false]));
+
+    self::assertSame(["--opt"], args::from_array(["--opt"]));
+    self::assertSame(["--opt", "value"], args::from_array(["--opt", "value"]));
+
+    self::assertSame([], args::from_array(["opt" => false]));
+    self::assertSame(["--opt"], args::from_array(["opt" => true]));
+    self::assertSame(["--opt", "value"], args::from_array(["opt" => "value"]));
+    self::assertSame(["--opt", "42"], args::from_array(["opt" => 42]));
+    self::assertSame(["--opt", "1", "2", "3", "--"], args::from_array(["opt" => [1, 2, 3]]));
+
+    self::assertSame(["x", "1", "2", "3", "y"], args::from_array(["x", [1, 2, 3], "y"]));
+  }
+}
diff --git a/wip/app/RunFile.php b/wip/app/RunFile.php
index 2ea5791..8afd663 100644
--- a/wip/app/RunFile.php
+++ b/wip/app/RunFile.php
@@ -269,6 +269,7 @@ class RunFile {
         "action_current_step" => 0,
       ];
     });
+    app2::_dispatch_signals();
   }
 
   /** indiquer qu'une étape est franchie dans l'action en cours */
diff --git a/wip/app/app2.php b/wip/app/app2.php
index bb07549..cbe4984 100644
--- a/wip/app/app2.php
+++ b/wip/app/app2.php
@@ -6,7 +6,6 @@ use nur\sery\cl;
 use nur\sery\ExitError;
 use nur\sery\os\path;
 use nur\sery\os\sh;
-use nur\sery\output\msg;
 use nur\sery\php\func;
 use nur\sery\str;
 use nur\sery\ValueException;
@@ -476,6 +475,10 @@ class app2 {
 
   #############################################################################
 
+  const EC_UNDEAD = 247;
+  const EC_REAPABLE = 248;
+  const EC_FORK_CHILD = 249;
+  const EC_FORK_PARENT = 250;
   const EC_DISABLED = 251;
   const EC_LOCKED = 252;
   const EC_BAD_COMMAND = 253;
@@ -536,4 +539,14 @@ class app2 {
       throw new ExitError(self::EC_DISABLED, "Planifications désactivées. La tâche n'a pas été lancée");
     }
   }
+
+  #############################################################################
+
+  static function action(?string $title, ?int $maxSteps=null): void {
+    self::get()->getRunfile()->action($title, $maxSteps);
+  }
+
+  static function step(int $nbSteps=1): void {
+    self::get()->getRunfile()->step($nbSteps);
+  }
 }
diff --git a/wip/app/args.php b/wip/app/args.php
new file mode 100644
index 0000000..c5179b9
--- /dev/null
+++ b/wip/app/args.php
@@ -0,0 +1,39 @@
+<?php
+namespace nur\sery\wip\app;
+
+use nur\sery\A;
+use nur\sery\str;
+
+class args {
+  /**
+   * transformer une liste d'argument de la forme
+   * - ["myArg" => $value]  devient  ["--my-arg", "$value"]
+   * - ["myOpt" => true]    devient  ["--my-opt"]
+   * - ["myOpt" => false]   est omis
+   * - les autres valeurs sont prises telles quelles
+   */
+  static function from_array(?array $array): array {
+    $args = [];
+    if ($array === null) return $args;
+    $index = 0;
+    foreach ($array as $arg => $value) {
+      if ($value === false) continue;
+      if ($arg === $index) {
+        $index++;
+      } else {
+        $arg = str::us2camel($arg);
+        $arg = str::camel2us($arg, false, "-");
+        $arg = str_replace("_", "-", $arg);
+        $args[] = "--$arg";
+        if (is_array($value)) $value[] = "--";
+        elseif ($value === true) $value = null;
+      }
+      if (is_array($value)) {
+        A::merge($args, array_map("strval", $value));
+      } elseif ($value !== null) {
+        $args[] = "$value";
+      }
+    }
+    return $args;
+  }
+}
diff --git a/wip/app/cli/bg_launcher.php b/wip/app/cli/bg_launcher.php
index 559fd79..98b2bfa 100644
--- a/wip/app/cli/bg_launcher.php
+++ b/wip/app/cli/bg_launcher.php
@@ -1,5 +1,119 @@
 <?php
 namespace nur\sery\wip\app\cli;
 
+use nur\sery\ExitError;
+use nur\sery\file\TmpfileWriter;
+use nur\sery\os\path;
+use nur\sery\os\proc\Cmd;
+use nur\sery\output\msg;
+use nur\sery\StateException;
+use nur\sery\wip\app\app2;
+use nur\sery\wip\app\args;
+use nur\sery\wip\app\RunFile;
+
 class bg_launcher {
+  /**
+   * transformer une liste d'argument de la forme
+   * - ["myArg" => $value]  devient  ["--my-arg", "$value"]
+   * - ["myOpt" => true]    devient  ["--my-opt"]
+   * - ["myOpt" => false]   est momis
+   * - les valeurs séquentielles sont prises telles quelles
+   */
+  static function verifix_args(array $args): array {
+    $args = args::from_array($args);
+    # corriger le chemin de l'application pour qu'il soit absolu et normalisé
+    $args[0] = path::abspath($args[0]);
+    return $args;
+  }
+
+  static function launch(string $appClass, array $args): int {
+    $app = app2::get();
+    $vendorBindir = $app->getVendorbindir();
+    $launch_php = "$vendorBindir/_launch.php";
+    if (!file_exists($launch_php)) {
+      $launch_php = __DIR__."/../../lib/_launch.php";
+    }
+    $tmpfile = new TmpfileWriter();
+    $tmpfile->keep()->serialize($app->getParams());
+
+    $args = self::verifix_args($args);
+    $cmd = new Cmd([
+      $launch_php,
+      "--internal-use", $tmpfile->getFile(),
+      $appClass, "--", ...$args,
+    ]);
+    $cmd->addRedir("both", "/tmp/nulib_app_launcher-launch.log");
+    $cmd->passthru($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->warnIfLocked()) return false;
+    $pid = pcntl_fork();
+    if ($pid == -1) {
+      # parent, impossible de forker
+      throw new ExitError(app2::EC_FORK_PARENT, "Unable to fork");
+    } elseif ($pid) {
+      # parent, fork ok
+      return true;
+    } else {
+      ## child, fork ok
+      # Créer un groupe de process, pour pouvoir tuer tous les enfants en même temps
+      $runfile->tm_startPg();
+      $logfile = $runfile->getLogfile() ?? "/tmp/NULIB_APP_app_start.log";
+      $pid = posix_getpid();
+      $exitcode = app2::EC_FORK_CHILD;
+      try {
+        # puis lancer la commande
+        $cmd = new Cmd($args);
+        $cmd->addSource("/g/init.env");
+        $cmd->addRedir("both", $logfile, true);
+        msg::debug("$pid: launching\n".$cmd->getCmd());
+        $cmd->fork_exec($exitcode);
+        msg::debug("$pid: exitcode=$exitcode");
+        return true;
+      } finally {
+        $runfile->wfStopped($exitcode);
+      }
+    }
+  }
+
+  static function _stop(Runfile $runfile): void {
+    $data = $runfile->read();
+    $pid = $data["pg_pid"];
+    if ($pid === null) {
+      msg::warning("$data[name]: groupe de process inconnu");
+      return;
+    }
+    msg::action("kill $pid");
+    if (!posix_kill(-$pid, SIGKILL)) {
+      switch (posix_get_last_error()) {
+      case PCNTL_ESRCH:
+        msg::afailure("process inexistant");
+        break;
+      case PCNTL_EPERM:
+        msg::afailure("process non accessible");
+        break;
+      case PCNTL_EINVAL:
+        msg::afailure("signal invalide");
+        break;
+      }
+      return;
+    }
+    $timeout = 10;
+    while ($runfile->tm_isUndead($pid)) {
+      sleep(1);
+      if (--$timeout == 0) {
+        msg::afailure("impossible d'arrêter la tâche");
+        return;
+      }
+    }
+    $runfile->wfStopped(app2::EC_REAPABLE);
+    msg::asuccess();
+  }
 }
diff --git a/wip/app/launcher.php b/wip/app/launcher.php
deleted file mode 100644
index 4d4a299..0000000
--- a/wip/app/launcher.php
+++ /dev/null
@@ -1,137 +0,0 @@
-<?php
-namespace nur\sery\wip\app;
-
-use nur\sery\app\Runfile;
-use nur\sery\cl;
-use nur\sery\file\TmpfileWriter;
-use nur\sery\os\path;
-use nur\sery\os\proc\Cmd;
-use nur\sery\output\msg;
-use nur\sery\StateException;
-use nur\sery\str;
-use nur\sery\wip\app\app2;
-
-class launcher {
-  /**
-   * transformer une liste d'argument de la forme
-   * - ["myArg" => $value]  devient  ["--my-arg", "$value"]
-   * - ["myOpt" => true]    devient  ["--my-opt"]
-   * - ["myOpt" => false]   est momis
-   * - les valeurs séquentielles sont prises telles quelles
-   */
-  static function verifix_args(array $args): array {
-    if (!cl::is_list($args)) {
-      $fixedArgs = [];
-      $index = 0;
-      foreach ($args as $arg => $value) {
-        if ($arg === $index) {
-          $index++;
-          $fixedArgs[] = $value;
-          continue;
-        } elseif ($value === false) {
-          continue;
-        }
-        $arg = str::us2camel($arg);
-        $arg = str::camel2us($arg, false, "-");
-        $arg = str_replace("_", "-", $arg);
-        $fixedArgs[] = "--$arg";
-        if ($value !== true) $fixedArgs[] = "$value";
-      }
-      $args = $fixedArgs;
-    }
-    # corriger le chemin de l'application pour qu'il soit absolu et normalisé
-    $args[0] = path::abspath($args[0]);
-    return $args;
-  }
-
-  static function launch(string $appClass, array $args): int {
-    $app = app2::get();
-    $vendorBindir = $app->getVendorbindir();
-    $launch_php = "$vendorBindir/_launch.php";
-    if (!file_exists($launch_php)) {
-      $launch_php = __DIR__."/../../lib/_launch.php";
-    }
-    $tmpfile = new TmpfileWriter();
-    $tmpfile->keep()->serialize($app->getParams());
-
-    $args = self::verifix_args($args);
-    $cmd = new Cmd([
-      $launch_php,
-      "--internal-use", $tmpfile->getFile(),
-      $appClass, "--", ...$args,
-    ]);
-    $cmd->addRedir("both", "/tmp/nulib_app_launcher-launch.log");
-    $cmd->passthru($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->warnIfLocked()) return false;
-    $pid = pcntl_fork();
-    if ($pid == -1) {
-      # parent, impossible de forker
-      throw new StateException("unable to fork");
-    } elseif ($pid) {
-      # parent, fork ok
-      return true;
-    } else {
-      ## child, fork ok
-      # Créer un groupe de process, pour pouvoir tuer tous les enfants en même temps
-      $runfile->tm_startPg();
-      $logfile = $runfile->getLogfile() ?? "/tmp/nulib_app_launcher-_start.log";
-      $pid = posix_getpid();
-      $exitcode = -776;
-      try {
-        # puis lancer la commande
-        $cmd = new Cmd($args);
-        $cmd->addSource("/g/init.env");
-        $cmd->addRedir("both", $logfile, true);
-        msg::debug("$pid: launching\n".$cmd->getCmd());
-        $cmd->fork_exec($exitcode);
-        msg::debug("$pid: exitcode=$exitcode");
-        return true;
-      } finally {
-        $runfile->wfStopped($exitcode);
-      }
-    }
-  }
-
-  static function _stop(Runfile $runfile): void {
-    $data = $runfile->read();
-    $pid = $data["pg_pid"];
-    if ($pid === null) {
-      msg::warning("$data[name]: groupe de process inconnu");
-      return;
-    }
-    msg::action("kill $pid");
-    if (!posix_kill(-$pid, SIGKILL)) {
-      switch (posix_get_last_error()) {
-      case PCNTL_ESRCH:
-        msg::afailure("process inexistant");
-        break;
-      case PCNTL_EPERM:
-        msg::afailure("process non accessible");
-        break;
-      case PCNTL_EINVAL:
-        msg::afailure("signal invalide");
-        break;
-      }
-      return;
-    }
-    $timeout = 10;
-    while ($runfile->tm_isUndead($pid)) {
-      sleep(1);
-      if (--$timeout == 0) {
-        msg::afailure("impossible d'arrêter la tâche");
-        return;
-      }
-    }
-    $runfile->wfStopped(-778);
-    msg::asuccess();
-  }
-}