How to get parent PID of a given process in GNU/Linux from command line?

Question

Resolved before asked: cat /proc/1111/status | grep PPid

Answer 1

Command line:

ps -o ppid= -p 1111

Function:

ppid () { ps -p ${1:-$$} -o ppid=; }

Alias (a function is preferable):

alias ppid='ps -o ppid= -p'

Script:

#!/bin/sh
pid=$1
if [ -z $pid ]
then
    read -p "PID: " pid
fi
ps -p ${pid:-$$} -o ppid=

If no PID is supplied to the function or the script, they default to show the PPID of the current process.

To use the alias, a PID must be supplied.

Answer 2

To print parent ids (PPID) of all the processes, use this command:

ps j

For the single process, just pass the PID, like: ps j 1234.

To extract only the value, filter output by awk, like:

ps j | awk 'NR>1 {print $3}' # BSD ps
ps j | awk 'NR>1 {print $1}' # GNU ps

---

To list PIDs of all parents, use pstree (install it if you don't have it):

$ pstree -sg 1234
systemd(1)───sshd(1036)───bash(2383)───pstree(3007)

---

To get parent PID of the current process, use echo $$.

Answer 3

This is one of those things I learn, forget, relearn, repeat. But it's useful. The pstree command's ‘s’ flag shows a tree with a leaf at N:

pstree -sA $(pgrep badblocks)
systemd---sudo---mkfs.ext4---badblocks

Answer 4

Parent pid is in shell variable PPID, so

echo $PPID

Answer 5

Read /proc/$PID/status. Can be easily scripted:

#!/bin/sh
P=$1
if [ -z "$P" ]; then
    read P
fi
cat /proc/"$P"/status | grep PPid: | grep -o "[0-9]*"

Answer 6

On Linux:

ps hoppid $thatprocess

Answer 7

$ ps -p $(ps -p $(echo $$) -o ppid=) -o comm=
    tmux

A little bit more complex example that checks the command of a parent that started current process Change comm= to cmd= to see full command

Answer 8

Run top with whatever options you want, like -u username and -p PID.

And while top is working press f, it shows a list of options you want to display in top output, and the displayed parameters will be shown in CAPITAL letters and the parameters which or not displaying will be shown in small letters.

So by entering the letter before the parameter you can enable or disable it. For parent process ID you have to enter b and then press Enter, it'll display the PPID in top output.

Answer 9

all parent processes of a pid

I came here when I was trying to find "all parent processes of a pid". I ended up making my own recursive function to do it.

pid_lineage.sh

#!/bin/bash -eu
main(){
  ps --pid ${1:-$$} --no-headers --format pid,ppid,args | 

    (
      read pid ppid args
      echo -e "$pid\t$args"
      [[ $pid -gt 1 ]] && main $ppid
    )
}
main "$@"

Answer 10

Here is a quick solution that should also work:

ps $$

Answer 11

Adding another way to do the same thing with ps. It seems this is sometimes the only way to get it done on certain Linux-based embedded devices.

ps -o ppid= -o pid= | grep MYPID

first column is the parent PID, second column is the child.