PowerOff is a simple Windows shutdown utility. You can easily shut down any machine running Windows XP by double-clicking the PowerOff icon on the desktop. PowerOff is actually a shortcut to shutdown. The command you are after is shutdown.This informs all users that the machine is going to be shutdown and tells all apps to close files etc. The command takes a parameter -h, -r or -s to shut down, restart or sleep the Mac. The command has to be run as root so you.

Close down the system at a given time.
Shutdown provides an automated shutdown procedure for super-users to nicely notify users when the system is shutting down, saving them from system administrators, hackers, and gurus, who would otherwise not bother with such niceties.

At intervals, becoming more frequent as apocalypse approaches and starting at ten hours before shutdown, warning messages are displayed on the terminals of all users logged in.

At shutdown time a message is written in the system log, containing the time of shutdown, who initiated the shutdown and the reason. A terminate signal is then sent to launchd to bring the system down to single-user state (depending on above options).

A scheduled shutdown can be canceled by killing the shutdown process (a SIGTERM should suffice).

FILES
/etc/nologin tells login not to let anyone log in
/fastboot tells rc(8) not to run fsck when rebooting
/usr/libexec/upsshutdown - Run a command when the UPS shuts down.

Examples

Reboot the machine immediately:
$ sudo shutdown -r now

Send the machine to sleep in 30 minutes:
$ sudo shutdown -s +30

Shutdown the machine in 60 minutes:
$ sudo shutdown -h +60

Cancel any of the above:
$ sudo killall shutdown

“Do all men kill the things they do not love?” ~ The Merchant of Venice

Power Off Mac Terminal

Related macOS commands:

kill - Stop a process from running.
login - log into the computer.
osascript - shutdown/restart via AppleScript.
pmset - sleep now.
sudo poweroff
wall - write a message to users.
fastboot(8)
reboot - Stop and restart the system.
uptime - Show how long system has been running.

Poweroff Machine Virtualbox