Since this thing is on the innerwebs I suppose it should have a

[python_utils.git] / exec_utils.py

diff --git a/exec_utils.py b/exec_utils.py
index b4e88bda36361064591d2c336f787e4fb234ae37..ae406ef41e925ddbd9ba5483ca1312b5686449e3 100644 (file)
--- a/exec_utils.py
+++ b/exec_utils.py
@@ -1,52 +1,64 @@
 #!/usr/bin/env python3
 
+# © Copyright 2021-2022, Scott Gasch
+
+"""Helper methods concerned with executing subprocesses."""
+
 import atexit
 import logging
+import os
 import selectors
 import shlex
 import subprocess
 import sys
 from typing import List, Optional
 
-
 logger = logging.getLogger(__file__)
 
 
-def cmd_showing_output(command: str, ) -> int:
+def cmd_showing_output(
+    command: str,
+) -> int:
     """Kick off a child process.  Capture and print all output that it
     produces on stdout and stderr.  Wait for the subprocess to exit
     and return the exit value as the return code of this function.
 
     """
     line_enders = set([b'\n', b'\r'])
-    p = subprocess.Popen(
+    sel = selectors.DefaultSelector()
+    with subprocess.Popen(
         command,
         shell=True,
         bufsize=0,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
         universal_newlines=False,
-    )
-    sel = selectors.DefaultSelector()
-    sel.register(p.stdout, selectors.EVENT_READ)
-    sel.register(p.stderr, selectors.EVENT_READ)
-    stream_ends = 0
-    while stream_ends < 2:
-        for key, _ in sel.select():
-            char = key.fileobj.read(1)
-            if not char:
-                stream_ends += 1
-                continue
-            if key.fileobj is p.stdout:
-                sys.stdout.buffer.write(char)
-                if char in line_enders:
-                    sys.stdout.flush()
-            else:
-                sys.stderr.buffer.write(char)
-                if char in line_enders:
-                    sys.stderr.flush()
-    p.wait()
-    return p.returncode
+    ) as p:
+        sel.register(p.stdout, selectors.EVENT_READ)  # type: ignore
+        sel.register(p.stderr, selectors.EVENT_READ)  # type: ignore
+        done = False
+        while not done:
+            for key, _ in sel.select():
+                char = key.fileobj.read(1)  # type: ignore
+                if not char:
+                    sel.unregister(key.fileobj)
+                    if len(sel.get_map()) == 0:
+                        sys.stdout.flush()
+                        sys.stderr.flush()
+                        sel.close()
+                        done = True
+                if key.fileobj is p.stdout:
+                    # sys.stdout.buffer.write(char)
+                    os.write(sys.stdout.fileno(), char)
+                    if char in line_enders:
+                        sys.stdout.flush()
+                else:
+                    # sys.stderr.buffer.write(char)
+                    os.write(sys.stderr.fileno(), char)
+                    if char in line_enders:
+                        sys.stderr.flush()
+        p.wait()
+        return p.returncode
 
 
 def cmd_with_timeout(command: str, timeout_seconds: Optional[float]) -> int:
@@ -64,9 +76,7 @@ def cmd_with_timeout(command: str, timeout_seconds: Optional[float]) -> int:
     subprocess.TimeoutExpired: Command '['/bin/bash', '-c', '/bin/sleep 2']' timed out after 0.1 seconds
 
     """
-    return subprocess.check_call(
-        ["/bin/bash", "-c", command], timeout=timeout_seconds
-    )
+    return subprocess.check_call(["/bin/bash", "-c", command], timeout=timeout_seconds)
 
 
 def cmd(command: str, timeout_seconds: Optional[float] = None) -> str:
@@ -116,26 +126,27 @@ def run_silently(command: str, timeout_seconds: Optional[float] = None) -> None:
     )
 
 
-def cmd_in_background(
-        command: str, *, silent: bool = False
-) -> subprocess.Popen:
+def cmd_in_background(command: str, *, silent: bool = False) -> subprocess.Popen:
     args = shlex.split(command)
     if silent:
-        subproc = subprocess.Popen(args,
-                                   stdin=subprocess.DEVNULL,
-                                   stdout=subprocess.DEVNULL,
-                                   stderr=subprocess.DEVNULL)
+        subproc = subprocess.Popen(
+            args,
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
     else:
         subproc = subprocess.Popen(args, stdin=subprocess.DEVNULL)
 
     def kill_subproc() -> None:
         try:
             if subproc.poll() is None:
-                logger.info("At exit handler: killing {}: {}".format(subproc, command))
+                logger.info('At exit handler: killing %s (%s)', subproc, command)
                 subproc.terminate()
                 subproc.wait(timeout=10.0)
         except BaseException as be:
             logger.exception(be)
+
     atexit.register(kill_subproc)
     return subproc
 
@@ -150,4 +161,5 @@ def cmd_list(command: List[str]) -> str:
 
 if __name__ == '__main__':
     import doctest
+
     doctest.testmod()