OS X (Apple)

dscl . -create /Users/hadmin UniqueID 401

#!/bin/bash

if [ -z $1 ] ; then
	echo "usage: `basename $0` [username] [password] ([UID] optional) ([GID] optional)"
	exit 1
fi

USERNAME=$1
PASSWORD=$2
USERID=$3
GROUPID=$4

if [ `uname -r | cut -c1` = 8 ] ; then
	PATH='/NetInfo/root'
elif [ `uname -r | cut -c1` = 9 ] ; then
	PATH='/Local/Default'
else
	exit 1
fi

if [ -z $GROUPID ] || [ -z $UNIQUEID ] ; then
	GROUPID=0
	UNIQUEID=489
fi

checkUser ()
{
	if [[ `/usr/bin/dscl localhost list /Local/Default/Users | /usr/bin/grep "$USERNAME" | /usr/bin/grep -v "$USERNAME." | /usr/bin/grep -v ".$USERNAME"` == "$USERNAME" ]] ; then
		echo "the username '$USERNAME' already exists"
		exit 1
	fi
}

makeUser ()
{
	/usr/bin/sudo /usr/bin/dscl localhost create $PATH/Users/$USERNAME
	/usr/bin/sudo /usr/bin/dscl localhost create $PATH/Users/$USERNAME PrimaryGroupID 0
	/usr/bin/sudo /usr/bin/dscl localhost create $PATH/Users/$USERNAME UniqueID 0
	/usr/bin/sudo /usr/bin/dscl localhost create $PATH/Users/$USERNAME UserShell /bin/bash
	/usr/bin/sudo /usr/bin/dscl localhost passwd $PATH/Users/$USERNAME $PASSWORD
	/usr/bin/sudo /usr/bin/dscl localhost append $PATH/Groups/admin GroupMembership $USERNAME
}

moveUser ()
{
    /bin/echo "creating new admin account homedir..."
	/bin/mkdir -p /var/home/$USERNAME
	/usr/bin/ditto -rsrc -V /System/Library/User\ Template/English.lproj/ /var/home/$USERNAME/
	/usr/sbin/chown -Rf $USERNAME:admin /var/home/$USERNAME
	/bin/echo "confirming what we just did..."
	/bin/ls /var/home/$USERNAME/
	/usr/bin/id $USERNAME
	/bin/echo "if that looks good, we're all set."
}	

deleteUser ()
{
	/usr/bin/sudo /usr/bin/dscl localhost delete $PATH/Users/$USERNAME
	/usr/bin/sudo /usr/bin/dscl localhost delete $PATH/Groups/admin GroupMembership $USERNAME
}

hideUser ()
{
	/usr/bin/sudo /bin/cp -n /Library/Preferences/com.apple.loginwindow.plist /Library/Preferences/com.apple.loginwindow.plist.backup
	/usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow Hide500Users -bool TRUE
	/usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow HiddenUsersList -array $USERNAME
	/usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.loginwindow SHOWOTHERUSERS_MANAGED -bool FALSE
}

checkUser
makeUser
moveUser
hideUser
#deleteUser