#!/bin/sh
#
# 2016 Daniel Heule (hda at sfs.biz)
# Copyright 2017, Philippe Gregoire <pg@pgregoire.xyz>
#
# This file is part of cdist.
#
# cdist is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# cdist is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with cdist. If not, see <http://www.gnu.org/licenses/>.
#
#
# Returns the process name of pid 1 ( normaly the init system )
# for example at linux this value is "init" or "systemd" in most cases
#

case $(uname -s) in
    Linux)
        if test -d /proc/1/
        then
            comm_name=$(cat /proc/1/comm)
        else
            # BusyBox's versions of ps and pgrep do not support some options
            # depending on which compile-time options have been used.
            # Both pgrep and ps are tried to get the command name
            comm_name=$(
                pgrep -P0 -l 2>/dev/null | awk '/^1[ \t]/ { print $2 }'
                || ps -o comm= -p 1 2>/dev/null)
        fi

        case $comm_name
        in
            systemd)
                echo systemd
            ;;
            init)
                # It could be anything...

                if test -h /proc/1/exe
                then
                    init_exe=/proc/1/exe
                else
                    init_exe=$(command -v "$comm_name")
                fi

                test -x "$comm_exe" || exit 1

                case $("$comm_exe" --version | head -n 1)
                in
                    *SysV*)
                        echo init
                    ;;
                    *upstart*)
                        echo upstart
                    ;;
                    *)
                        echo ""
                    ;;
                esac
        esac
    ;;
    FreeBSD|OpenBSD)
        ps -o comm= -p 1 2>/dev/null || true
    ;;
    Darwin)
        basename "$(ps -o comm= -p 1 2>/dev/null)"
    ;;
    *)
        # return a empty string as unknown value
        echo ""
    ;;
esac