Implement handling of KeyboardInterrupt

This commit adds handling of KeyboardInterrupts. For this purpose, a
    signal handler is installed for all processes and a global variable
    that calls further cleanup steps. Because processes are used, each
    process receives the SIGINT. To properly stop and not just wait for
    something to handle the SIGINT, each process raises a custom
    `CleanupRequired` error and exits.

music-normalize/main.py

@@ -10,7 +10,7 @@ import ffmpy
 import argparse
 
 # multiprocessing stuff
-from multiprocessing import Pool
+from multiprocessing import Pool, Value, parent_process
 
 # executing some commands
 import subprocess
@@ -38,6 +38,12 @@ import pyloudnorm
 # file copy
 import shutil
 
+# signal handling
+import signal
+
+# exiting
+import sys
+
 """
 Normalize loudness of all music files in a given directory and its subdirectories.
 """
@@ -45,6 +51,18 @@ Normalize loudness of all music files in a given directory and its subdirectorie
 musicfile_extensions = (".flac", ".wav", ".mp3", ".m4a", ".aac", ".opus")
 
 
+class CleanupRequired(Exception):
+    pass
+
+
+def sigint_handler(signum, frame):
+    # set workers to clean up
+    cleanup_required.value = 1
+    # Output only once
+    if parent_process() is None:
+        print("\nReceived KeyboardInterrupt. Process cleaning up and stopping...")
+
+
 def loudnorm(inputfile: str, outputfile: str):
     """
     Normalize audio to EBU R 128 standard using pyloudnorm
@@ -59,6 +77,10 @@ def loudnorm(inputfile: str, outputfile: str):
     meter = pyloudnorm.Meter(rate=rate)
     loudness = meter.integrated_loudness(data=data)
 
+    # cleanup check
+    if bool(cleanup_required.value):
+        raise CleanupRequired()
+
     # normalize audio
     file_normalized = pyloudnorm.normalize.loudness(
         data=data, input_loudness=loudness, target_loudness=-18.0
@@ -76,6 +98,9 @@ def ffmpeg_to_wav(inputfile: str, outputfile: str):
         inputfile (str): Path to input file
         outputfile (str): Path to output file
     """
+    # cleanup check
+    if bool(cleanup_required.value):
+        raise CleanupRequired()
 
     # convert to wav in temporary directory
     with tempfile.TemporaryDirectory() as tempdir:
@@ -99,6 +124,10 @@ def ffmpeg_to_wav(inputfile: str, outputfile: str):
 
         subprocess.run(ff.cmd, shell=True, capture_output=True)
 
+        # cleanup check
+        if bool(cleanup_required.value):
+            raise CleanupRequired()
+
         # normalize loudness
         loudnorm(inputfile=temp_input, outputfile=temp_output)
 
@@ -107,6 +136,10 @@ def ffmpeg_to_wav(inputfile: str, outputfile: str):
             outputfile: "-c:a libopus" " " "-b:a 192k" " " "-compression_level 10"
         }
 
+        # cleanup check
+        if bool(cleanup_required.value):
+            raise CleanupRequired()
+
         ff = ffmpy.FFmpeg(
             inputs={temp_output: None}, outputs=outputcmd, global_options=("-y")
         )
@@ -123,6 +156,9 @@ def ffmpeg_copy_metadata(inputfile: str, outputfile: str):
         inputfile (str): Path to input file
         outputfile (str): Path to output file
     """
+    # cleanup check
+    if bool(cleanup_required.value):
+        raise CleanupRequired()
 
     # store output file as temporary file. FFMPEG can't work on files in-place
     with tempfile.NamedTemporaryFile() as temp_audio:
@@ -154,10 +190,13 @@ def main(inputfile: str) -> Optional[list[Any]]:
     Output:
         dynamically normalised audio files (list)
     """
-
     # set output folder to parent path + "normalized"
     outputfolder = os.path.join(os.path.dirname(inputfile), "normalized")
 
+    # cleanup check
+    if bool(cleanup_required.value):
+        raise CleanupRequired()
+
     # NOTE create output folder
     # because multiple parallel processes are at work here,
     # there might be conflicts with one trying to create the directory although it already exists
@@ -201,6 +240,11 @@ if __name__ == "__main__":
     """
     Handle arguments and other details for interactive usage
     """
+    # global cleanup variable
+    cleanup_required = Value("i", 0)
+
+    # handle KeyboardInterrupt
+    signal.signal(signal.SIGINT, sigint_handler)
 
     # start time of program
     starttime = time.time()
@@ -265,8 +309,11 @@ if __name__ == "__main__":
                 if os.path.getmtime(filepath) >= float(timeprev):
                     musicfiles.append(os.path.join(root, file))
 
+    # process pool
     with Pool(cpu) as p:
-        nonlinear_all: Optional[list[Any]] = p.map(main, musicfiles)
+        result = p.map_async(main, musicfiles)
+        # wait for all processes to finish
+        result.wait()
 
     # write this run's time into file
     with open(timefile, "w") as file: