X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=exec_utils.py;h=016310793152ddeb8872f5ec279c26ae1994655e;hb=36fea7f15ed17150691b5b3ead75450e575229ef;hp=0ed360191d6ad9f89c64acf591f78044008f4009;hpb=497fb9e21f45ec08e1486abaee6dfa7b20b8a691;p=python_utils.git

diff --git a/exec_utils.py b/exec_utils.py
index 0ed3601..0163107 100644
--- a/exec_utils.py
+++ b/exec_utils.py
@@ -1,45 +1,152 @@
 #!/usr/bin/env python3
 
+import atexit
+import logging
+import selectors
 import shlex
 import subprocess
-from typing import List
+import sys
+from typing import List, Optional
 
 
-def cmd_with_timeout(command: str, timeout_seconds: float) -> int:
+logger = logging.getLogger(__file__)
+
+
+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(
+        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()
+    sys.stdout.flush()
+    sys.stderr.flush()
+    return p.returncode
+
+
+def cmd_with_timeout(command: str, timeout_seconds: Optional[float]) -> int:
+    """Run a command but do not let it run for more than timeout seconds.
+    Doesn't capture or rebroadcast command output.  Function returns
+    the exit value of the command or raises a TimeoutExpired exception
+    if the deadline is exceeded.
+
+    >>> cmd_with_timeout('/bin/echo foo', 10.0)
+    0
+
+    >>> cmd_with_timeout('/bin/sleep 2', 0.1)
+    Traceback (most recent call last):
+    ...
+    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
     )
 
 
-def cmd(command: str) -> str:
-    """Run a command with everything encased in a string and return
-    the output text as a string.  Raises subprocess.CalledProcessError.
+def cmd(command: str, timeout_seconds: Optional[float] = None) -> str:
+    """Run a command and capture its output to stdout (only) in a string.
+    Return that string as this function's output.  Raises
+    subprocess.CalledProcessError or TimeoutExpired on error.
+
+    >>> cmd('/bin/echo foo')[:-1]
+    'foo'
+
+    >>> cmd('/bin/sleep 2', 0.1)
+    Traceback (most recent call last):
+    ...
+    subprocess.TimeoutExpired: Command '/bin/sleep 2' timed out after 0.1 seconds
+
     """
     ret = subprocess.run(
-        command, shell=True, capture_output=True, check=True
+        command,
+        shell=True,
+        capture_output=True,
+        check=True,
+        timeout=timeout_seconds,
     ).stdout
     return ret.decode("utf-8")
 
 
-def run_silently(command: str) -> None:
+def run_silently(command: str, timeout_seconds: Optional[float] = None) -> None:
     """Run a command silently but raise subprocess.CalledProcessError if
-    it fails."""
+    it fails.
+
+    >>> run_silently("/usr/bin/true")
+
+    >>> run_silently("/usr/bin/false")
+    Traceback (most recent call last):
+    ...
+    subprocess.CalledProcessError: Command '/usr/bin/false' returned non-zero exit status 1.
+
+    """
     subprocess.run(
-        command, shell=True, stderr=subprocess.DEVNULL, stdout=subprocess.DEVNULL,
-        capture_output=False, check=True
+        command,
+        shell=True,
+        stderr=subprocess.DEVNULL,
+        stdout=subprocess.DEVNULL,
+        capture_output=False,
+        check=True,
+        timeout=timeout_seconds,
     )
 
 
-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:
-        return 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:
-        return subprocess.Popen(args,
-                                stdin=subprocess.DEVNULL)
+        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)
+                )
+                subproc.terminate()
+                subproc.wait(timeout=10.0)
+        except BaseException as be:
+            logger.exception(be)
+
+    atexit.register(kill_subproc)
+    return subproc
 
 
 def cmd_list(command: List[str]) -> str:
@@ -48,3 +155,9 @@ def cmd_list(command: List[str]) -> str:
     """
     ret = subprocess.run(command, capture_output=True, check=True).stdout
     return ret.decode("utf-8")
+
+
+if __name__ == '__main__':
+    import doctest
+
+    doctest.testmod()