feat: Add a hidden way to access Fluent's stdout/stderr (#3504)

src/ansys/fluent/core/__init__.py

@@ -133,3 +133,11 @@ def version_info() -> str:
 
 # Whether to clear environment variables related to Fluent parallel mode
 CLEAR_FLUENT_PARA_ENVS = False
+
+# Set stdout of the launched Fluent process
+# Valid values are same as subprocess.Popen's stdout argument
+LAUNCH_FLUENT_STDOUT = None
+
+# Set stderr of the launched Fluent process
+# Valid values are same as subprocess.Popen's stderr argument
+LAUNCH_FLUENT_STDERR = None

src/ansys/fluent/core/launcher/launcher_utils.py

@@ -28,6 +28,10 @@ def _get_subprocess_kwargs_for_fluent(env: Dict[str, Any], argvals) -> Dict[str,
     kwargs: Dict[str, Any] = {}
     if is_slurm:
         kwargs.update(stdout=subprocess.PIPE)
+    else:
+        kwargs.update(
+            stdout=pyfluent.LAUNCH_FLUENT_STDOUT, stderr=pyfluent.LAUNCH_FLUENT_STDERR
+        )
     if is_windows():
         kwargs.update(shell=True, creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
     else:

src/ansys/fluent/core/launcher/standalone_launcher.py

@@ -177,6 +177,8 @@ def __init__(
         The allocated machines and core counts are queried from the scheduler environment and
         passed to Fluent.
         """
+        import ansys.fluent.core as pyfluent
+
         self.argvals, self.new_session = _get_argvals_and_session(locals().copy())
         self.file_transfer_service = file_transfer_service
         if os.getenv("PYFLUENT_SHOW_SERVER_GUI") == "1":
@@ -214,7 +216,9 @@ def __init__(
             self.argvals["topy"], self.argvals["journal_file_names"]
         )
 
-        if is_windows():
+        if is_windows() and not (
+            pyfluent.LAUNCH_FLUENT_STDOUT or pyfluent.LAUNCH_FLUENT_STDERR
+        ):
             # Using 'start.exe' is better; otherwise Fluent is more susceptible to bad termination attempts.
             self._launch_cmd = 'start "" ' + self._launch_string
         else:
@@ -231,7 +235,7 @@ def __call__(self):
         try:
             logger.debug(f"Launching Fluent with command: {self._launch_cmd}")
 
-            subprocess.Popen(self._launch_cmd, **self._kwargs)
+            process = subprocess.Popen(self._launch_cmd, **self._kwargs)
 
             try:
                 _await_fluent_launch(
@@ -247,7 +251,7 @@ def __call__(self):
                     logger.warning(
                         f"Retrying Fluent launch with less robust command: {launch_cmd}"
                     )
-                    subprocess.Popen(launch_cmd, **self._kwargs)
+                    process = subprocess.Popen(launch_cmd, **self._kwargs)
                     _await_fluent_launch(
                         self._server_info_file_name,
                         self.argvals["start_timeout"],
@@ -264,6 +268,7 @@ def __call__(self):
                 launcher_args=self.argvals,
                 inside_container=False,
             )
+            session._process = process
             start_watchdog = _confirm_watchdog_start(
                 self.argvals["start_watchdog"],
                 self.argvals["cleanup_on_exit"],