下面是一个参考的Shell脚本程序，可以输出指定进程的进程层次结构：

#!/bin/bash

# get the pid of the specified process
if [ "$1" == "" ]; then
    echo "Usage: $0 "
    exit
fi
TARGET_PID="$1"

# function to get the parent pid of the specified pid
function get_parent_pid() {
    local pid="$1"
    # get the parent pid of the specified pid
    local ppid=`ps -o ppid= -p $pid`
    # if no parent pid is found, set parent pid to 0
    if [ "$ppid" == "" ]; then
        ppid=0
    fi
    echo $ppid
}

# print the process hierarchy
echo "process hierarchy of PID $TARGET_PID:"
while [ "$TARGET_PID" != "1" ]; do
    # get the name of the specified pid
    NAME=`ps -o comm= -p $TARGET_PID`
    # output the pid and name of the specified pid
    echo "    PID $TARGET_PID ($NAME)"
    # get the parent pid of the specified pid
    TARGET_PID=`get_parent_pid $TARGET_PID`
done
echo "    PID 1 (systemd)"

以上Shell脚本程序使用ps命令获取指定进程ID（pid）的父进程ID（ppid），并依次向上查找父进程直到PID为1为止，输出进程层次结构。如果运行以上程序时没有指定指定进程ID，则使用说明将被输出。