cs.psutils 20240211

Assorted process and subprocess management functions.

Assorted process and subprocess management functions.

Latest release 20240211:

• run: new optional input= parameter to presupply input data.
• New prep_argv(*argv) function to flatten and trim computes argv lists; use automatically in run(), pipeot(), pipefrom().

Not to be confused with the excellent (psutil)[https://pypi.org/project/psutil/] package.

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 from MAX_ARGV: 131072
• 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, *, quiet=False, text=True, stdin=-3, **popen_kw)

Pipe text (usually) from a command using subprocess.Popen. Return the Popen object with .stdout as a pipe.

Parameters:

• argv: the command argument list
• quiet: optional flag, default False; if true, print the command to stderr
• text: optional flag, default True; passed to Popen.
• stdin: optional value for Popen's stdin, default DEVNULL Other keyword arguments are passed to Popen.

Note that argv is passed through prep_argv before use, allowing direct invocation with conditional parts. See the prep_argv function for details.

Function pipeto(argv, *, quiet=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.

Note that argv is passed through prep_argv before use, allowing direct invocation with conditional parts. See the prep_argv function for details.

Function prep_argv(*argv)

A trite list comprehension to reduce an argument list *argv to the entries which are not None or False and to flatten other entries which are not strings.

This exists ease the construction of argument lists with methods like this:

>>> command_exe = 'hashindex'
>>> hashname = 'sha1'
>>> quiet = False
>>> verbose = True
>>> prep_argv(
...     command_exe,
...     quiet and '-q',
...     verbose and '-v',
...     hashname and ('-h', hashname),
... )
['hashindex', '-v', '-h', 'sha1']

where verbose is a bool governing the -v option and hashname is either str to be passed with -h hashname or None to omit the option.

Function print_argv(*argv, indent='', subindent=' ', end='\n', file=None, fold=False)

Print an indented possibly folded command line.

Function remove_pidfile(path)

Truncate and remove a pidfile, permissions permitting.

Function run(argv, *, doit=True, logger=None, quiet=True, input=None, stdin=None, **subp_options)

Run a command via subprocess.run. Return the CompletedProcess result or None if doit is false.

Parameters:

• argv: the command line to run
• doit: optional flag, default True; if false do not run the command and return None
• logger: optional logger, default None; if True, use logging.getLogger(); if not None or False trace using print_argv
• quiet: default True; if false, print the command and its output
• input: default None: alternative to stdin; passed to subprocess.run
• stdin: standard input for the subprocess, default subprocess.DEVNULL; passed to subprocess.run
• subp_options: optional mapping of keyword arguments to pass to subprocess.run

Note that argv is passed through prep_argv before use, allowing direct invocation with conditional parts. See the prep_argv function for details.

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 20240211:

• run: new optional input= parameter to presupply input data.
• New prep_argv(*argv) function to flatten and trim computes argv lists; use automatically in run(), pipeot(), pipefrom().

Release 20231129: run(): default stdin=subprocess.DEVNULL.

Release 20230612:

• pipefrom: default stdin=DEVNULL.
• Make many parameters keyword only.

Release 20221228:

• signal_handlers: bugfix iteration of sig_hnds.
• Use cs.gimmicks instead of cs.logutils.
• Drop use of cs.upd, fixes circular import; users of run() may need to call "with Upd().above()" themselves.

Release 20221118: run: do not print cp.stdout.

Release 20220805: run: print trace to stderr.

Release 20220626: run: default quiet=True.

Release 20220606:

• run: fold in the superior run() from cs.ebooks.
• pipefrom,pipeto: replace trace= with quiet= like run().
• print_argv: add an end parameter (used by pipefrom).

Release 20220531:

• New print_argv function for writing shell command lines out nicely.
• Bump requirements for cs.gimmicks.

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.