diff --git a/.github/workflows/qleverfiles-check.yml b/.github/workflows/qleverfiles-check.yml
index 528beb14..4cda5f8d 100644
--- a/.github/workflows/qleverfiles-check.yml
+++ b/.github/workflows/qleverfiles-check.yml
@@ -33,6 +33,7 @@ jobs:
       - name: Check that all the files in `src/qlever/Qleverfiles` parse.
         working-directory: ${{github.workspace}}/qlever-control
         run: |
+          export QLEVER_ARGCOMPLETE_ENABLED=1
           for QLEVERFILE in src/qlever/Qleverfiles/Qleverfile.*; do
             echo
             echo -e "\x1b[1;34mChecking ${QLEVERFILE}\x1b[0m"
diff --git a/src/qlever/Qleverfiles/Qleverfile.dblp b/src/qlever/Qleverfiles/Qleverfile.dblp
index d7e90937..574d1192 100644
--- a/src/qlever/Qleverfiles/Qleverfile.dblp
+++ b/src/qlever/Qleverfiles/Qleverfile.dblp
@@ -17,7 +17,7 @@ FORMAT       = ttl
 
 [index]
 INPUT_FILES      = *.gz
-MULTI_INPUT_JSON = $$(ls *.gz | xargs -I {} echo '{ "cmd": "zcat {}" }')
+MULTI_INPUT_JSON = { "cmd": "zcat {}", "for-each": "*.gz" }
 SETTINGS_JSON    = { "ascii-prefixes-only": false, "num-triples-per-batch": 5000000, "prefixes-external": [""] }
 
 [server]
diff --git a/src/qlever/commands/add_text_index.py b/src/qlever/commands/add_text_index.py
index 15fa647b..f2401878 100644
--- a/src/qlever/commands/add_text_index.py
+++ b/src/qlever/commands/add_text_index.py
@@ -64,7 +64,7 @@ def execute(self, args) -> bool:
         # Show the command line.
         self.show(add_text_index_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # When running natively, check if the binary exists and works.
         if args.system == "native":
@@ -74,6 +74,7 @@ def execute(self, args) -> bool:
                 log.error(f"Running \"{args.index_binary}\" failed ({e}), "
                           f"set `--index-binary` to a different binary or "
                           f"use `--container_system`")
+                return False
 
         # Check if text index files already exist.
         existing_text_index_files = get_existing_index_files(
diff --git a/src/qlever/commands/cache_stats.py b/src/qlever/commands/cache_stats.py
index 28eb6e58..5b618a98 100644
--- a/src/qlever/commands/cache_stats.py
+++ b/src/qlever/commands/cache_stats.py
@@ -47,7 +47,7 @@ def execute(self, args) -> bool:
         self.show("\n".join([cache_stats_cmd, cache_settings_cmd]),
                   only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Execute them.
         try:
diff --git a/src/qlever/commands/clear_cache.py b/src/qlever/commands/clear_cache.py
index 448aeb39..8732120c 100644
--- a/src/qlever/commands/clear_cache.py
+++ b/src/qlever/commands/clear_cache.py
@@ -48,7 +48,7 @@ def execute(self, args) -> bool:
                                 f"\"{args.access_token}\"")
         self.show(clear_cache_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Execute the command.
         try:
@@ -76,5 +76,7 @@ def execute(self, args) -> bool:
         # Show cache stats.
         log.info("")
         args.detailed = False
-        CacheStatsCommand().execute(args)
+        if not CacheStatsCommand().execute(args):
+            log.error("Clearing the cache was successful, but showing the "
+                      "cache stats failed {e}")
         return True
diff --git a/src/qlever/commands/example_queries.py b/src/qlever/commands/example_queries.py
index c38b8678..dff44ba0 100644
--- a/src/qlever/commands/example_queries.py
+++ b/src/qlever/commands/example_queries.py
@@ -197,7 +197,7 @@ def execute(self, args) -> bool:
             only_show=args.show,
         )
         if args.show:
-            return False
+            return True
 
         # Get the example queries.
         try:
@@ -229,8 +229,11 @@ def execute(self, args) -> bool:
             if args.clear_cache == "yes":
                 args.server_url = sparql_endpoint
                 args.complete = False
+                clear_cache_successful = False
                 with mute_log():
-                    ClearCacheCommand().execute(args)
+                    clear_cache_successful = ClearCacheCommand().execute(args)
+                if not clear_cache_successful:
+                    log.warn("Failed to clear the cache")
 
             # Remove OFFSET and LIMIT (after the last closing bracket).
             if args.remove_offset_and_limit or args.limit:
diff --git a/src/qlever/commands/get_data.py b/src/qlever/commands/get_data.py
index 4ae2bb7d..b27eca5f 100644
--- a/src/qlever/commands/get_data.py
+++ b/src/qlever/commands/get_data.py
@@ -31,7 +31,7 @@ def execute(self, args) -> bool:
         # Construct the command line and show it.
         self.show(args.get_data_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Execute the command line.
         try:
diff --git a/src/qlever/commands/index.py b/src/qlever/commands/index.py
index 81babea1..2ca8aaff 100644
--- a/src/qlever/commands/index.py
+++ b/src/qlever/commands/index.py
@@ -239,7 +239,7 @@ def execute(self, args) -> bool:
         # Show the command line.
         self.show(f"{settings_json_cmd}\n{index_cmd}", only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # When running natively, check if the binary exists and works.
         if args.system == "native":
diff --git a/src/qlever/commands/index_stats.py b/src/qlever/commands/index_stats.py
index 975576ac..b997b8c7 100644
--- a/src/qlever/commands/index_stats.py
+++ b/src/qlever/commands/index_stats.py
@@ -18,32 +18,45 @@ def __init__(self):
         pass
 
     def description(self) -> str:
-        return ("Breakdown of the time and space used for the index build")
+        return "Breakdown of the time and space used for the index build"
 
     def should_have_qleverfile(self) -> bool:
         return False
 
-    def relevant_qleverfile_arguments(self) -> dict[str: list[str]]:
+    def relevant_qleverfile_arguments(self) -> dict[str : list[str]]:
         return {"data": ["name"]}
 
     def additional_arguments(self, subparser) -> None:
-        subparser.add_argument("--only-time", action="store_true",
-                               default=False,
-                               help="Show only the time used")
-        subparser.add_argument("--only-space", action="store_true",
-                               default=False,
-                               help="Show only the space used")
-        subparser.add_argument("--ignore-text-index", action="store_true",
-                               default=False,
-                               help="Ignore the text index")
-        subparser.add_argument("--time-unit",
-                               choices=["s", "min", "h", "auto"],
-                               default="auto",
-                               help="The time unit")
-        subparser.add_argument("--size-unit",
-                               choices=["B", "MB", "GB", "TB", "auto"],
-                               default="auto",
-                               help="The size unit")
+        subparser.add_argument(
+            "--only-time",
+            action="store_true",
+            default=False,
+            help="Show only the time used",
+        )
+        subparser.add_argument(
+            "--only-space",
+            action="store_true",
+            default=False,
+            help="Show only the space used",
+        )
+        subparser.add_argument(
+            "--ignore-text-index",
+            action="store_true",
+            default=False,
+            help="Ignore the text index",
+        )
+        subparser.add_argument(
+            "--time-unit",
+            choices=["s", "min", "h", "auto"],
+            default="auto",
+            help="The time unit",
+        )
+        subparser.add_argument(
+            "--size-unit",
+            choices=["B", "MB", "GB", "TB", "auto"],
+            default="auto",
+            help="The size unit",
+        )
 
     def execute_time(self, args, log_file_name) -> bool:
         """
@@ -65,8 +78,9 @@ def execute_time(self, args, log_file_name) -> bool:
                 with open(text_log_file_name, "r") as text_log_file:
                     lines.extend(text_log_file.readlines())
         except Exception as e:
-            log.error(f"Problem reading text index log file "
-                      f"{text_log_file_name}: {e}")
+            log.error(
+                f"Problem reading text index log file " f"{text_log_file_name}: {e}"
+            )
             return False
 
         # Helper function that finds the next line matching the given `regex`,
@@ -95,12 +109,14 @@ def find_next_line(regex, update_current_line=True):
                 if regex_match:
                     try:
                         return datetime.strptime(
-                                re.match(timestamp_regex, line).group(),
-                                timestamp_format), regex_match
+                            re.match(timestamp_regex, line).group(), timestamp_format
+                        ), regex_match
                     except Exception as e:
-                        log.error(f"Could not parse timestamp of form "
-                                  f"\"{timestamp_regex}\" from line "
-                                  f" \"{line.rstrip()}\" ({e})")
+                        log.error(
+                            f"Could not parse timestamp of form "
+                            f'"{timestamp_regex}" from line '
+                            f' "{line.rstrip()}" ({e})'
+                        )
             # If we get here, we did not find a matching line.
             if not update_current_line:
                 current_line = current_line_backup
@@ -119,26 +135,32 @@ def find_next_line(regex, update_current_line=True):
             # file (old format: "Creating a pair" + names of permutations in
             # line "Writing meta data for ..."; new format: name of
             # permutations already in line "Creating permutations ...").
-            perm_begin, _ = find_next_line(r"INFO:\s*Creating a pair",
-                                           update_current_line=False)
+            perm_begin, _ = find_next_line(
+                r"INFO:\s*Creating a pair", update_current_line=False
+            )
             if perm_begin is None:
                 perm_begin, perm_info = find_next_line(
                     r"INFO:\s*Creating permutations ([A-Z]+ and [A-Z]+)",
-                    update_current_line=False)
+                    update_current_line=False,
+                )
             else:
                 _, perm_info = find_next_line(
                     r"INFO:\s*Writing meta data for ([A-Z]+ and [A-Z]+)",
-                    update_current_line=False)
+                    update_current_line=False,
+                )
             if perm_info is None:
                 break
             perm_begin_and_info.append((perm_begin, perm_info))
-        convert_end = (perm_begin_and_info[0][0] if
-                       len(perm_begin_and_info) > 0 else None)
+        convert_end = (
+            perm_begin_and_info[0][0] if len(perm_begin_and_info) > 0 else None
+        )
         normal_end, _ = find_next_line(r"INFO:\s*Index build completed")
-        text_begin, _ = find_next_line(r"INFO:\s*Adding text index",
-                                       update_current_line=False)
-        text_end, _ = find_next_line(r"INFO:\s*Text index build comp",
-                                     update_current_line=False)
+        text_begin, _ = find_next_line(
+            r"INFO:\s*Adding text index", update_current_line=False
+        )
+        text_end, _ = find_next_line(
+            r"INFO:\s*Text index build comp", update_current_line=False
+        )
         if args.ignore_text_index:
             text_begin = text_end = None
 
@@ -147,9 +169,11 @@ def find_next_line(regex, update_current_line=True):
             log.error("Missing line that index build has started")
             return False
         if overall_begin and not merge_begin:
-            log.error("According to the log file, the index build "
-                      "has started, but is still in its first "
-                      "phase (parsing the input)")
+            log.error(
+                "According to the log file, the index build "
+                "has started, but is still in its first "
+                "phase (parsing the input)"
+            )
             return False
 
         # Helper function that shows the duration for a phase (if the start and
@@ -187,22 +211,24 @@ def show_duration(heading, start_end_pairs):
         show_duration("Convert to global IDs", [(convert_begin, convert_end)])
         for i in range(len(perm_begin_and_info)):
             perm_begin, perm_info = perm_begin_and_info[i]
-            perm_end = perm_begin_and_info[i + 1][0] if i + 1 < len(
-                    perm_begin_and_info) else normal_end
-            perm_info_text = (perm_info.group(1).replace(" and ", " & ")
-                              if perm_info else f"#{i + 1}")
-            show_duration(f"Permutation {perm_info_text}",
-                          [(perm_begin, perm_end)])
+            perm_end = (
+                perm_begin_and_info[i + 1][0]
+                if i + 1 < len(perm_begin_and_info)
+                else normal_end
+            )
+            perm_info_text = (
+                perm_info.group(1).replace(" and ", " & ") if perm_info else f"#{i + 1}"
+            )
+            show_duration(f"Permutation {perm_info_text}", [(perm_begin, perm_end)])
         show_duration("Text index", [(text_begin, text_end)])
         if text_begin and text_end:
             log.info("")
-            show_duration("TOTAL time",
-                          [(overall_begin, normal_end),
-                           (text_begin, text_end)])
+            show_duration(
+                "TOTAL time", [(overall_begin, normal_end), (text_begin, text_end)]
+            )
         elif normal_end:
             log.info("")
-            show_duration("TOTAL time",
-                          [(overall_begin, normal_end)])
+            show_duration("TOTAL time", [(overall_begin, normal_end)])
         return True
 
     def execute_space(self, args) -> bool:
@@ -252,24 +278,29 @@ def show_size(heading, size):
         return True
 
     def execute(self, args) -> bool:
-        ret_value = args.show
+        return_value = True
 
         # The "time" part of the command.
         if not args.only_space:
             log_file_name = f"{args.name}.index-log.txt"
-            self.show(f"Breakdown of the time used for "
-                      f"building the index, based on the timestamps for key "
-                      f"lines in \"{log_file_name}\"", only_show=args.show)
+            self.show(
+                f"Breakdown of the time used for "
+                f"building the index, based on the timestamps for key "
+                f'lines in "{log_file_name}"',
+                only_show=args.show,
+            )
             if not args.show:
-                ret_value &= self.execute_time(args, log_file_name)
+                return_value &= self.execute_time(args, log_file_name)
             if not args.only_time:
                 log.info("")
 
         # The "space" part of the command.
         if not args.only_time:
-            self.show("Breakdown of the space used for building the index",
-                      only_show=args.show)
+            self.show(
+                "Breakdown of the space used for building the index",
+                only_show=args.show,
+            )
             if not args.show:
-                ret_value &= self.execute_space(args)
+                return_value &= self.execute_space(args)
 
-        return ret_value
+        return return_value
diff --git a/src/qlever/commands/log.py b/src/qlever/commands/log.py
index 3b2599b4..816072bc 100644
--- a/src/qlever/commands/log.py
+++ b/src/qlever/commands/log.py
@@ -47,10 +47,20 @@ def execute(self, args) -> bool:
         log_cmd += f" {log_file}"
         self.show(log_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Execute the command.
         log.info(f"Follow log file {log_file}, press Ctrl-C to stop"
                  f" following (will not stop the server)")
         log.info("")
-        subprocess.run(log_cmd, shell=True)
+        try:
+            subprocess.run(log_cmd, shell=True)
+            return True
+        except Exception as e:
+            log.error(e)
+            return False
+
+
+
+
+
diff --git a/src/qlever/commands/query.py b/src/qlever/commands/query.py
index 163c0c8a..979cd5a5 100644
--- a/src/qlever/commands/query.py
+++ b/src/qlever/commands/query.py
@@ -53,7 +53,7 @@ def execute(self, args) -> bool:
                     f" --data-urlencode query={shlex.quote(args.query)}")
         self.show(curl_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Launch query.
         try:
diff --git a/src/qlever/commands/setup_config.py b/src/qlever/commands/setup_config.py
index 6cff7822..0eff3b23 100644
--- a/src/qlever/commands/setup_config.py
+++ b/src/qlever/commands/setup_config.py
@@ -60,7 +60,7 @@ def execute(self, args) -> bool:
         setup_config_cmd += "> Qleverfile"
         self.show(setup_config_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # If there is already a Qleverfile in the current directory, exit.
         qleverfile_path = Path("Qleverfile")
diff --git a/src/qlever/commands/start.py b/src/qlever/commands/start.py
index e51717b5..4b6ae8f6 100644
--- a/src/qlever/commands/start.py
+++ b/src/qlever/commands/start.py
@@ -72,7 +72,9 @@ def execute(self, args) -> bool:
         if args.kill_existing_with_same_port:
             args.cmdline_regex = f"^ServerMain.* -p {args.port}"
             args.no_containers = True
-            StopCommand().execute(args)
+            if not StopCommand().execute(args):
+                log.error("Stopping the existing server failed")
+                return False
             log.info("")
 
         # Construct the command line based on the config file.
@@ -115,7 +117,7 @@ def execute(self, args) -> bool:
         # Show the command line.
         self.show(start_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # When running natively, check if the binary exists and works.
         if args.system == "native":
@@ -192,6 +194,7 @@ def execute(self, args) -> bool:
                 run_command(curl_cmd)
             except Exception as e:
                 log.error(f"Setting the index description failed ({e})")
+                return False
         if args.text_description:
             text_desc = args.text_description
             curl_cmd = (f"curl -Gs http://localhost:{port}/api"
@@ -202,6 +205,7 @@ def execute(self, args) -> bool:
                 run_command(curl_cmd)
             except Exception as e:
                 log.error(f"Setting the text description failed ({e})")
+                return False
 
         # Kill the tail process. NOTE: `tail_proc.kill()` does not work.
         tail_proc.terminate()
@@ -209,7 +213,9 @@ def execute(self, args) -> bool:
         # Execute the warmup command.
         if args.warmup_cmd and not args.no_warmup:
             log.info("")
-            WarmupCommand().execute(args)
+            if not WarmupCommand().execute(args):
+                log.error("Warmup failed")
+                return False
 
         # Show cache stats.
         log.info("")
diff --git a/src/qlever/commands/status.py b/src/qlever/commands/status.py
index 5d066660..a8efed54 100644
--- a/src/qlever/commands/status.py
+++ b/src/qlever/commands/status.py
@@ -35,7 +35,7 @@ def execute(self, args) -> bool:
                   f"the command line matches {args.cmdline_regex}"
                   f" using Python's psutil library", only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Show the results as a table.
         num_processes_found = 0
@@ -47,3 +47,4 @@ def execute(self, args) -> bool:
                 num_processes_found += 1
         if num_processes_found == 0:
             print("No processes found")
+        return True
diff --git a/src/qlever/commands/stop.py b/src/qlever/commands/stop.py
index f2f8e80a..82225304 100644
--- a/src/qlever/commands/stop.py
+++ b/src/qlever/commands/stop.py
@@ -49,7 +49,7 @@ def execute(self, args) -> bool:
                             f"\"{args.server_container}\"")
         self.show(description, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # First check if there is container running and if yes, stop and remove
         # it (unless the user has specified `--no-containers`).
@@ -90,14 +90,12 @@ def execute(self, args) -> bool:
                     return False
                 return True
 
-        # No matching process found.
+        # If no matching process found, show a message and the output of the
+        # status command.
         message = "No matching process found" if args.no_containers else \
                   "No matching process or container found"
         log.error(message)
-
-        # Show output of status command.
         args.cmdline_regex = "^ServerMain.* -i [^ ]*"
         log.info("")
         StatusCommand().execute(args)
-
-        return False
+        return True
diff --git a/src/qlever/commands/system_info.py b/src/qlever/commands/system_info.py
index 0d1ed167..1e45d1bd 100644
--- a/src/qlever/commands/system_info.py
+++ b/src/qlever/commands/system_info.py
@@ -58,7 +58,7 @@ def execute(self, args) -> bool:
         # Say what the command is doing.
         self.show("Show system information and Qleverfile", only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Show system information.
         show_heading("System Information")
diff --git a/src/qlever/commands/ui.py b/src/qlever/commands/ui.py
index b4baa248..23dea87a 100644
--- a/src/qlever/commands/ui.py
+++ b/src/qlever/commands/ui.py
@@ -70,8 +70,10 @@ def execute(self, args) -> bool:
             "\n".join(["Stop running containers", pull_cmd, run_cmd, exec_cmd]),
             only_show=args.show,
         )
-        if qlever_is_running_in_container or args.show:
+        if qlever_is_running_in_container:
             return False
+        if args.show:
+            return True
 
         # Stop running containers.
         for container_system in Containerize.supported_systems():
diff --git a/src/qlever/commands/warmup.py b/src/qlever/commands/warmup.py
index 7a7041fb..49150262 100644
--- a/src/qlever/commands/warmup.py
+++ b/src/qlever/commands/warmup.py
@@ -30,7 +30,7 @@ def execute(self, args) -> bool:
         # Show what the command is doing.
         self.show(args.warmup_cmd, only_show=args.show)
         if args.show:
-            return False
+            return True
 
         # Execute the command.
         try: