daemon-loop 0.0.3

simple CLI utility to run other programs periodically as daemon without cron

Daemon Loop

Daemon loop is simple and clean CLI utility to run programs periodically.

It's better alternative to running commands like:

while true; do date >> date.log; sleep 5; done 

(or even running such commands in screen/tmux sessions)

Installation

pip3 install daemon-loop

Usage

usage: loop [-h] [-n N] [-p PERIOD] [--log FILENAME] [-e] [-v] [-d]
            command [command ...]

Run command in loop (with features)

positional arguments:
  command               command with arguments

optional arguments:
  -h, --help            show this help message and exit
  -n N                  Run N times and exit (default: 0 = infinite)
  -p PERIOD, --period PERIOD
                        Run every N seconds (default: 60)
  --log FILENAME        Write command stdout to this file
  -e, --err             Write command stderr to logfile)
  -v, --verbose         Write loop technical info to logfile)
  -d, --daemon          Work as daemon

Example usage

Simple and almost useless - run date every second until Ctrl-C:

$ loop date
Sun Dec 20 05:18:21 +07 2020
Sun Dec 20 05:19:21 +07 2020
Sun Dec 20 05:20:21 +07 2020
^C

Run date +%s (print unixtime) 3 times every 10 seconds and quit

$ loop -p 10 -n 3 -- date +%s
1608416485
1608416495
1608416505

And now something more useful - make our date program a daemon!

$ loop -dvep 10 --log /tmp/loop.log -- date +%s
$ pidof -x loop
25934

• -d: run as daemon
• -v: include technical info about time of start/stop, status code and daemon pid
• -e (--err): include stderr to logfile
• -p (--period): period is 10 seconds
• --log: logfile

log file will look like this:

# 2020-12-20 05:39:01 my pid: 25934 run: date +%s
1608417541
# 2020-12-20 05:39:01 finished with status 0

# 2020-12-20 05:39:11 my pid: 25934 run: date +%s
1608417551
# 2020-12-20 05:39:11 finished with status 0

Caveats

If --daemon used, loop will chdir to '/'. Loop will automatically adjust path to logfile and executable, but you should care about other parameters. For example, command loop -d -- touch myfile started from user home will touch /myfile (in root), and most likely will fail.