hoshinotsuyoshi and nateberkopec `ps -p` will check correctly whether $PID exists (#1545)
It is appropriate to use `ps -p` in that place.

Under certain conditions, existing code ``[ "`ps -A -o pid=
| grep -c $PID`" -eq 0 ]`` may behave incorrectly.

For example, if the content of $PID happens to be a short string
(such as `199`), and another process includes the string
(process such as `2199`), then unfortunately `grep -c` will return
positive number even if `199` is not running.
Latest commit 9aea96e Mar 28, 2018

README.md

Puma as a service

Upstart

See /tools/jungle/upstart for Ubuntu's upstart scripts.

Systemd

See /docs/systemd.

Init.d

Deprecatation Warning : init.d was replaced by systemd since Debian 8 and Ubuntu 16.04, you should look into /docs/systemd unless you are on an older OS.

See /tools/jungle/init.d for tools to use with init.d and start-stop-daemon.

rc.d

See /tools/jungle/rc.d for FreeBSD's rc.d scripts