#!/usr/bin/env python3

# proc2log: new processes monitor

import os
import argparse
from time import sleep

parser = argparse.ArgumentParser()
parser.add_argument(
    '-p', 
    '--period', 
    help='peroid in seconds between proc checks, default value: 0.1', 
    default=0.1, 
    type=float
    )
args = parser.parse_args()
period = args.period

unknown_name = '<unknown>'


# получение чистого пид сета
def foo():
    proc_list = os.listdir('/proc')
    proc_set = set()
    for i in proc_list:
        if i.isdigit() != True:
            continue
        proc_set.add(i)
    return proc_set


# имя через пид
def pid_to_name(pid):
    try:
        with open('/proc/' + pid + '/status') as f:
            for line in f:
                return line[:-1].split('\t')[1]
    except FileNotFoundError:
        return unknown_name


# печать одного пида и имени
def print_pid(pid):

    try:
        with open('/proc/' + pid + '/status') as f:
            for lineno, line in enumerate(f):
                name = line[:-1].split('\t')[1]
                print('+ {}, {}'.format(pid, name))
                pid_dict[pid] = name
                if lineno >= 0:
                    break

    except FileNotFoundError:
        name = pid_dict.pop(pid, unknown_name)
        print('                         - {}, {}'.format(pid, name))

    except ProcessLookupError:
        name = pid_dict.pop(pid, unknown_name)
        print('                         - {}, {}'.format(pid, name))


# нахождение и печать дельт сетов
def delta(old_set):

    new_set = set(os.listdir('/proc'))
    plus = new_set - old_set
    minus = old_set - new_set

    if len(plus) > 0:
        for pid in plus:
            print_pid(pid)

    if len(minus) > 0:
        for pid in minus:
            print_pid(pid)

    return new_set


print('proc2log started with period {} seconds'.format(period))
print('+ PID, NAME              - PID, NAME')

# первичное наполнение словаря значениями pid:name для печати имён исчезнувших процессов
pid_dict = dict()
for pid in foo():
    pid_dict[pid] = pid_to_name(pid)

pid_set = set(os.listdir('/proc'))
try:
    while True:
        pid_set = delta(pid_set)
        sleep(period)
except KeyboardInterrupt:
    exit()