diff --git a/src/duct.py b/src/duct.py
index bd02f806..f4308984 100755
--- a/src/duct.py
+++ b/src/duct.py
@@ -140,9 +140,6 @@ def serialize(self):
 
 
 def create_and_parse_args():
-    now = datetime.now()
-    # 'pure' iso 8601 does not make good filenames
-    file_safe_iso = now.strftime("%Y-%m-%d.%H-%M-%S")
     parser = argparse.ArgumentParser(
         description="Gathers metrics on a command and all its child processes."
     )
@@ -157,8 +154,8 @@ def create_and_parse_args():
     parser.add_argument(
         "--output-prefix",
         type=str,
-        default=os.getenv("DUCT_OUTPUT_PREFIX", f".duct/run-logs/{file_safe_iso}"),
-        help="Directory in which all logs will be saved.",
+        default=os.getenv("DUCT_OUTPUT_PREFIX", "{file_safe_iso}"),
+        help="`path+fileprefix` or directory in which all logs will be saved.",
     )
     parser.add_argument(
         "--report-interval",
@@ -246,12 +243,16 @@ def monitor_process(
             break
 
         elapsed_time = time.time() - report.start_time
-        report.collect_sample()
+        sep = "" if output_prefix.endswith(os.sep) else "-"
+        resource_stats_log_path = "{output_prefix}{sep}{pid}-resource-usage.json"
         if elapsed_time >= (report.number + 1) * report_interval:
             aggregated = report.aggregate_samples()
             for pid, pinfo in aggregated.items():
                 with open(
-                    f"{output_prefix}/{pid}_resource_usage.json", "a"
+                    resource_stats_log_path.format(
+                        output_prefix=output_prefix, sep=sep, pid=pid
+                    ),
+                    "a",
                 ) as resource_statistics_log:
                     pinfo["elapsed_time"] = elapsed_time
                     resource_statistics_log.write(json.dumps(aggregated))
@@ -261,20 +262,20 @@ def monitor_process(
 
 def prepare_outputs(capture_outputs, outputs, output_prefix):
     if capture_outputs in ["all", "stdout"] and outputs in ["all", "stdout"]:
-        stdout = TeeStream(f"{output_prefix}/stdout.txt")
+        stdout = TeeStream(f"{output_prefix}stdout")
         stdout.start()
     elif capture_outputs in ["all", "stdout"] and outputs in ["none", "stderr"]:
-        stdout = open(f"{output_prefix}/stdout.txt")
+        stdout = open(f"{output_prefix}stdout")
     elif capture_outputs in ["none", "stderr"] and outputs in ["all", "stdout"]:
         stdout = subprocess.PIPE
     else:
         stdout = subprocess.DEVNULL
 
     if capture_outputs in ["all", "stderr"] and outputs in ["all", "stderr"]:
-        stderr = TeeStream(f"{output_prefix}/stderr.txt")
+        stderr = TeeStream(f"{output_prefix}stderr")
         stderr.start()
     elif capture_outputs in ["all", "stderr"] and outputs in ["none", "stdout"]:
-        stderr = open(f"{output_prefix}/stderr.txt")
+        stderr = open(f"{output_prefix}/stderr")
     elif capture_outputs in ["none", "stdout"] and outputs in [
         "all",
         "stderr",
@@ -285,15 +286,37 @@ def prepare_outputs(capture_outputs, outputs, output_prefix):
     return stdout, stderr
 
 
+def format_output_prefix(output_prefix_template):
+    f_kwargs = {}
+    if "file_safe_iso" in output_prefix_template:
+        # 'pure' iso 8601 does not make good filenames
+        f_kwargs["file_safe_iso"] = datetime.now().strftime("%Y-%m-%d.%H-%M-%S")
+    if f_kwargs:
+        return output_prefix_template.format(**f_kwargs)
+    else:
+        return output_prefix_template
+
+
+def ensure_directories(path):
+    if path.endswith(os.sep):  # If it ends in "/" (for linux) treat as a dir
+        os.makedirs(path, exist_ok=True)
+    else:
+        # Path does not end with a separator, treat the last part as a filename
+        directory = os.path.dirname(path)
+        if directory:  # If there's a directory part, create it
+            os.makedirs(directory, exist_ok=True)
+
+
 def main():
     """A wrapper to execute a command, monitor and log the process details."""
     args = create_and_parse_args()
-    os.makedirs(args.output_prefix, exist_ok=True)
+    formatted_output_prefix = format_output_prefix(args.output_prefix)
+    ensure_directories(formatted_output_prefix)
     stdout, stderr = prepare_outputs(
-        args.capture_outputs, args.outputs, args.output_prefix
+        args.capture_outputs, args.outputs, formatted_output_prefix
     )
     process = subprocess.Popen(
-        [str(args.command)] + args.arguments.copy(),
+        [str(args.command)] + args.arguments,
         stdout=stdout,
         stderr=stderr,
         preexec_fn=os.setsid,
@@ -311,7 +334,7 @@ def main():
             process,
             args.report_interval,
             args.sample_interval,
-            args.output_prefix,
+            formatted_output_prefix,
         ]
         monitoring_thread = threading.Thread(
             target=monitor_process, args=monitoring_args
@@ -320,10 +343,9 @@ def main():
         monitoring_thread.join()
 
     if args.record_types in ["all", "system-summary"]:
-        with open(
-            f"{args.output_prefix}/system-report.session-{report.session_id}.json",
-            "a",
-        ) as system_logs:
+        sep = "" if formatted_output_prefix.endswith(os.sep) else "-"
+        system_info_path = f"{formatted_output_prefix}{sep}info.json"
+        with open(system_info_path, "a") as system_logs:
             report.end_time = time.time()
             report.run_time_seconds = f"{report.end_time - report.start_time}"
             report.get_system_info()