How to get all parent processes and all subprocesses with `pstree` - linux

Question

Command pstree PID can show all subprocess information of the process specified by PID. However, I also want to know all parent process information of the process PID, how can I get it?
An example:
init
|- parent_process
| `- current_process
| |- subprocess_1
| `- subprocess_2
`- other_process
What I want is when I run pstree current_process_pid, I want to get below output:
init
`- parent_process
`- current_process
|- subprocess_1
`- subprocess_2
When I run pstree subprocess_1_pid, it will output:
init
`- parent_process
`- current_process
`- subprocess_1

Answer 1

# With my psmisc 22.20:
pstree -p -s PID
Maybe if with ps -ef:
awk -vPID=$1 '
function getParent ( pid ) {
if (pid == "" || pid == "0") return;
while ("ps -ef | grep "pid | getline) {
if ($2 == pid) {
print $8"("$2") Called By "$3;
getParent($3);
break;
}
}
close ("ps -ef")
}
BEGIN { getParent(PID) }
'
This is ugly assuming ps output column and order. Actually one single run of ps -ef contains all info needed.
This don't worth the time, I still recommend updating psmisc, it won't hurt.
EDIT: A mimic using single run ps -ef:
ps -ef | awk -vPID=$1 '
function getpp ( pid, pcmd, proc ) {
for ( p in pcmd ) {
if (p == pid) {
getpp(proc[p], pcmd, proc);
if (pid != PID) printf("%s(%s)───", pcmd[pid], pid);
}
}
}
NR > 1 {
# pid=>cmd
pcmd[$2] = $8;
# pid=>Parent
pproc[$2] = $3;
}
END {
getpp(PID, pcmd, pproc);
printf "\n";
system("pstree -p "PID);
}'

Answer 2

I found laps options mentioned by #haridsv (pstree -laps <pid>) being a solution. It was a bit verbose for me though, so I'd stick to a shorter aps output.
To get the process tree of the current process (its ID is $$ in Bash):
pstree -aps $$
That prints the process tree like this:
systemd,1
└─kitty,86739
└─bash,86742
└─pstree,86904 -aps 86742