I'm using ps -eo ppid,pid,cmd to view all process, and how can I format the output to view like below?
Only given PID and its ancestor will print (until init).
23464 current
|
23211 bash
|
23210 sshd: xxW
|
23193 sshd: WWcccv
|
728 /usr/sbin/sshd –D
|
1 init
I'm writing a script to view ancestral process using PID without using pstree, if possible.
Maybe something like:
#! /bin/bash -
pid=${1?Please give a pid}
sep=
while
[ "$pid" -gt 0 ] &&
read -r ppid name < <(ps -o ppid= -o args= -p "$pid")
do
printf "$sep%$((3+${#pid}/2))d%$((4-${#pid}/2))s%s\n" "$pid" "" "$name"
sep=$' |\n'
pid=$ppid
done
Which gives:
$ that-script "$$"
13612 /bin/zsh
|
4137 SCREEN screen -xRS main
|
4136 screen screen -xRS main
|
4130 zsh
|
4128 xterm
|
1 /sbin/init splash
That's a bit sluggish as it runs one ps per process in the ancestry. You can improve it by running ps to retrieve all the information at once and post process it with awk for instance:
#! /bin/sh -
pid=${1?Please give a pid}
ps -Ao pid= -o ppid= -o args= |
awk -v p="$pid" '
{
pid = $1; ppid[pid] = $2
sub(/([[:space:]]*[[:digit:]]+){2}[[:space:]]*/, "")
args[pid] = $0
}
END {
while (p) {
printf "%s%*d%*s%s\n", sep, 3+length(p)/2, p, 4-length(p)/2, "", args[p]
p = ppid[p]
sep = " |\n"
}
}'
What about using pstree -spa ? It will show both predecessors and ancestors for the given pid, including pid and command lines.
$ pstree -spa 3056
systemd,1
└─upowerd,3056
├─{gdbus},3071
└─{gmain},3069
pstree -spa $$ uses the shell's PID as a start
Place pid, ppid's into array. Recursive function or loops to walk through the array, printing only the desired pid and ppid entries.