How to know if a process is running?

Question

linux

To track file changes on the disk I use:
https://github.com/gregghz/Watcher
When I run it, everything works, but over time, it stops working.
I restart it and it works again
How to check that it is working at the current moment?
1) I check pid, it exists:

[email protected]:~$ll /root/.watcher/watcher.pid
-rw-rw-rw- 1 root root 5 июн  3 08:38 /root/.watcher/watcher.pid

2) I check the processes:

[email protected]:~$ps ax | grep watcher
1980 ?        Sl     0:01 python /usr/bin/watcher.py start
3198 pts/0    S+     0:00 grep watcher

I run it through rc-local.service, for this I created a file

/etc/rc.local#!/bin/sh -e
watcher.py stop
watcher.py start
exit 0

PS. "watcher.py stop" registered, because sometimes it gives an error that it is already running. Probably looks that PID is created.
Created a service, registered in the file
/etc/systemd/system/rc-local.service

[Unit]
 Description=/etc/rc.local Compatibility
 ConditionPathExists=/etc/rc.local
 
[Service]
 Type=forking
 ExecStart=/etc/rc.local start
 TimeoutSec=0
 StandardOutput=tty
 RemainAfterExit=yes
 SysVStartPriority=99
 
[Install]
WantedBy=multi-user.target

Gave him rights and set to run:

chmod +x /etc/rc.local
systemctl enable rc-local
systemctl start rc-local

PS. I think to put it on daily reboot in cron. But while it is interesting how to trace its "fall".

Answer 1

why crowns and other crutches, if there is a systemd ??
write the appropriate unit and systemd itself will start the process and restart in case of a crash.

Answer 2

run via supervisord.

Answer 3

Is using incron without python binding not an option?

Answer 4

You can use the universal cross-platform solution - psutil (pip install psutil).

import psutil
for proc in psutil.process_iter():
    name = proc.name()
    print(name)
    if name == "program.exe":
        pass