Subprocess improvements (#10973)

* Use list-form arguments for subprocess.run calls where possible

Augments #10944

* Deduplicate curl code

* Avoid eval() to parse integer

---------

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

utils/downloads.py

@@ -26,8 +26,10 @@ def is_url(url, check=True):
 
 def gsutil_getsize(url=''):
     # gs://bucket/file size https://cloud.google.com/storage/docs/gsutil/commands/du
-    s = subprocess.check_output(f'gsutil du {url}', shell=True).decode('utf-8')
-    return eval(s.split(' ')[0]) if len(s) else 0  # bytes
+    output = subprocess.check_output(['gsutil', 'du', url], shell=True, encoding='utf-8')
+    if output:
+        return int(output.split()[0])
+    return 0
 
 
 def url_getsize(url='https://ultralytics.com/images/bus.jpg'):
@@ -36,6 +38,25 @@ def url_getsize(url='https://ultralytics.com/images/bus.jpg'):
     return int(response.headers.get('content-length', -1))
 
 
+def curl_download(url, filename, *, silent: bool = False) -> bool:
+    """
+    Download a file from a url to a filename using curl.
+    """
+    silent_option = 'sS' if silent else ''  # silent
+    proc = subprocess.run([
+        'curl',
+        '-#',
+        f'-{silent_option}L',
+        url,
+        '--output',
+        filename,
+        '--retry',
+        '9',
+        '-C',
+        '-',])
+    return proc.returncode == 0
+
+
 def safe_download(file, url, url2=None, min_bytes=1E0, error_msg=''):
     # Attempts to download file from url or url2, checks and removes incomplete downloads < min_bytes
     from utils.general import LOGGER
@@ -50,8 +71,8 @@ def safe_download(file, url, url2=None, min_bytes=1E0, error_msg=''):
         if file.exists():
             file.unlink()  # remove partial downloads
         LOGGER.info(f'ERROR: {e}\nRe-attempting {url2 or url} to {file}...')
-        subprocess.run(
-            f"curl -# -L '{url2 or url}' -o '{file}' --retry 3 -C -".split())  # curl download, retry and resume on fail
+        # curl download, retry and resume on fail
+        curl_download(url2 or url, file)
     finally:
         if not file.exists() or file.stat().st_size < min_bytes:  # check
             if file.exists():