get environment variables of running process in linux

Get the process ID using ps command

ps -ef | grep something

For example:

root@ubuntuserver:~# ps -ef |grep xfce4-session
user01      7363    7287  0 11:17 ?        00:00:00 xfce4-session
root       57795    7644  0 11:53 pts/0    00:00:00 grep --color=auto xfce4-session
root@ubuntuserver:~# 

Here the PID is 7363

Get environment variables from file /proc/PID/environ

root@ubuntuserver:~# cat /proc/7363/environ 
SHELL=/bin/bashQT_ACCESSIBILITY=1SSH_AUTH_SOCK=/tmp/ssh-JRT467Z6hAHp/agent.7287SSH_AGENT_PID=7354PWD=/home/user01LOGNAME=user01XDG_SESSION_TYPE=x11GPG_AGENT_INFO=/run/user/1002/gnupg/S.gpg-agent:0:1PULSE_SCRIPT=/etc/xrdp/pulse/default.paHOME=/home/user01LANG=en_US.UTF-8XRDP_SOCKET_PATH=/run/xrdp/sockdirXRDP_PULSE_SOURCE_SOCKET=xrdp_chansrv_audio_in_socket_10XDG_SESSION_CLASS=userUSER=user01XRDP_SESSION=1DISPLAY=:10.0XRDP_PULSE_SINK_SOCKET=xrdp_chansrv_audio_out_socket_10SHLVL=1XDG_SESSION_ID=c12XDG_RUNTIME_DIR=/run/user/1002XDG_DATA_DIRS=/usr/local/share:/usr/share:/var/lib/snapd/desktopPATH=/sbin:/bin:/usr/bin:/usr/local/bin:/snap/binDBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1002/busUID=1002_=/bin/xfce4-sessionroot@ubuntuserver:~#

/proc/[pid]/environ
      This file contains the environment for the process.  The entries
      are separated by null bytes ('\0'), and there may be a null byte
      at  the  end.

Print out environment variables

root@ubuntuserver:~# strings /proc/7363/environ 
SHELL=/bin/bash
QT_ACCESSIBILITY=1
...
SSH_AUTH_SOCK=/tmp/ssh-JRT467Z6hAHp/agent.7287
UID=1002
root@ubuntuserver:~#

OR

root@ubuntuserver:~# cat /proc/7363/environ | tr '\000' '\n'
SHELL=/bin/bash
QT_ACCESSIBILITY=1
...
SSH_AUTH_SOCK=/tmp/ssh-JRT467Z6hAHp/agent.7287
UID=1002
root@ubuntuserver:~#

See snippet of man proc

/proc/[pid]/environ
      This  file contains the initial environment that was set when the currently exe‐
      cuting program was started via execve(2).  The entries  are  separated  by  null
      bytes  ('\0'),  and there may be a null byte at the end.  Thus, to print out the
      environment of process 1, you would do:

      $ cat /proc/1/environ | tr '\000' '\n'