How do I get the parent process ID of a given child process in Linux.

Use

ps -o ppid=

e.g. ps -o ppid= 2076 returns 2054, which you can easily use in a script etc. ps -o ppid= -C foo gives the PPID of process with command foo. You can also use the old fashioned ps | grep: ps -eo ppid,comm | grep '[f]oo'.

Fuller explanation: ps -f 2072 returns

UID        PID  PPID  C STIME TTY      STAT   TIME CMD
izx       2076  2054  0 07:16 ?        S      0:00 /usr/lib/pulseaudio/pulse/gconf-helper

The pstree relation is: pstree -s -p 2076:

init(1)───pulseaudio(2054)───gconf-helper(2076)

Step 2:-

echo $PPID

if you need the command from this parent pid:

cat /proc/$PPID/comm

if you need the full command line (with all options):

cat /proc/$PPID/cmdline

$PPID is defined by the shell, it’s the PID of the parent process
in /proc/, you have some dirs with the PID of each processes. Then, if you cat /proc/$PPID/comm, you echo the command name of the PID

That’s it for now !