Assorted process and subprocess management functions.

Latest release 20220504: signal_handlers: reshape try/except to avoid confusing traceback.

Function groupargv(pre_argv, argv, post_argv=(), max_argv=None, encode=False)

Distribute the array argv over multiple arrays to fit within MAX_ARGV. Return a list of argv lists.

Parameters:

• pre_argv: the sequence of leading arguments
• argv: the sequence of arguments to distribute; this may not be empty
• post_argv: optional, the sequence of trailing arguments
• max_argv: optional, the maximum length of each distributed argument list, default: MAX_ARGV
• encode: default False. If true, encode the argv sequences into bytes for accurate tallying. If encode is a Boolean, encode the elements with their .encode() method. If encode is a str, encode the elements with their .encode() method with encode as the encoding name; otherwise presume that encode is a callable for encoding each element.

The returned argv arrays will contain the encoded element values.

Function PidFileManager(path, pid=None)

Context manager for a pid file.

Parameters:

• path: the path to the process id file.
• pid: the process id to store in the pid file, default from os.etpid.

Writes the process id file at the start and removes the process id file at the end.

Function pipefrom(argv, trace=False, binary=False, keep_stdin=False, **kw)

Pipe text from a command. Optionally trace invocation. Return the Popen object with .stdout decoded as text.

Parameters:

• argv: the command argument list
• binary: if true (default false) return the raw stdout instead of a text wrapper
• trace: if true (default False), if trace is True, recite invocation to stderr otherwise presume that trace is a stream to which to recite the invocation.
• keep_stdin: if true (default False) do not attach the command's standard input to the null device. The default behaviour is to do so, preventing commands from accidentally consuming the main process' input stream.

Other keyword arguments are passed to the io.TextIOWrapper which wraps the command's output.

Function pipeto(argv, trace=False, **kw)

Pipe text to a command. Optionally trace invocation. Return the Popen object with .stdin encoded as text.

Parameters:

• argv: the command argument list
• trace: if true (default False), if trace is True, recite invocation to stderr otherwise presume that trace is a stream to which to recite the invocation.

Other keyword arguments are passed to the io.TextIOWrapper which wraps the command's input.

Function remove_pidfile(path)

Truncate and remove a pidfile, permissions permitting.

Function run(argv, logger=None, pids=None, **kw)

Run a command. Optionally trace invocation. Return result of subprocess.call.

Parameters:

• argv: the command argument list
• pids: if supplied and not None, call .add and .remove with the subprocess pid around the execution

Other keyword arguments are passed to subprocess.call.

Function signal_handler(sig, handler, call_previous=False)

Context manager to push a new signal handler, yielding the old handler, restoring the old handler on exit. If call_previous is true (default False) also call the old handler after the new handler on receipt of the signal.

Parameters:

• sig: the int signal number to catch
• handler: the handler function to call with (sig,frame)
• call_previous: optional flag (default False); if true, also call the old handler (if any) after handler

Function signal_handlers(sig_hnds, call_previous=False, _stacked=None)

Context manager to stack multiple signal handlers, yielding a mapping of sig=>old_handler.

Parameters:

• sig_hnds: a mapping of sig=>new_handler or an iterable of (sig,new_handler) pairs
• call_previous: optional flag (default False), passed to signal_handler()

Function stop(pid, signum=<Signals.SIGTERM: 15>, wait=None, do_SIGKILL=False)

Stop the process specified by pid, optionally await its demise.

Parameters:

• pid: process id. If pid is a string, treat as a process id file and read the process id from it.
• signum: the signal to send, default signal.SIGTERM.
• wait: whether to wait for the process, default None. If None, return True (signal delivered). If 0, wait indefinitely until the process exits as tested by os.kill(pid, 0). If greater than 0, wait up to wait seconds for the process to die; if it exits, return True, otherwise False;
• do_SIGKILL: if true (default False), send the process signal.SIGKILL as a final measure before return.

Function write_pidfile(path, pid=None)

Write a process id to a pid file.

Parameters:

• path: the path to the pid file.
• pid: the process id to write, defautl from os.getpid.

Release Log

Release 20220504: signal_handlers: reshape try/except to avoid confusing traceback.

Release 20220429:

• New signal_handler(sig,handler,call_previous=False) context manager to push a signal handler.
• New signal_handlers() context manager to stack handlers for multiple signals.

Release 20190101: Bugfix context manager cleanup. groupargv improvements.

Release 20171112: Bugfix array length counting.

Release 20171110: New function groupargv for breaking up argv lists to fit within the maximum argument limit; constant MAX_ARGV for the default limit.

Release 20171031: run: accept optional pids parameter, a setlike collection of process ids.

Release 20171018: run: replace trace parameter with logger, default None

Release 20170908.1: remove dependency on cs.pfx

Release 20170908: run: pass extra keyword arguments to subprocess.call

Release 20170906.1: Add run, pipefrom and pipeto - were incorrectly in another module.

Release 20170906: First PyPI release.