how to get all parent processes and all subprocesses by `pstree`

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

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);
}'