Linux pgrep active xsession - bash

Question

I'm writing a code which :
put all xsessions name in a file.
while not EOF , assign a line to a
variable, then pass it to pgrep, line by line.
Output pgrep in terminal.
There is several way to print the desktop environnement,session/window manager.
But i couldn't find one wich work for all xsession(/usr/share/xsessions).
After many try , it still doesn't work.
There is a problem with the loop.
ls /usr/share/xsessions/>all_xsessions;while [ "$var" != "" ]; do let x=x+1; var=$(sed "${x}q;d" all_xsessions); pgrep -lu $(whoami) $var; done

Answer 1

Unfortunately, there is no real standart way or universal environmental variable for that.
Most of information can be get from printenv but variable names differ a lot.
For example, in arch-linux with xfce, where sessions are run directly from windows-manager, you can get PID from $SESSION_MANAGER variable.
But in ubuntu, that is the most popular desktop distro now, your x-session is in fact upstart-session, that starts everything needed. And the variable is $UPSTART_SESSION.
And in xubuntu you have BOTH $SESSION_MANAGER and $UPSTART_SESSION variables.
There is also $DESKTOP_SESSION, it exists almost everywhere and contains some pretty name for desktop-environment, like xfce, ubuntu of xubuntu.
So, that can differ from distro to distro, but in most cases that script will work for you.
#!/bin/bash
[[ -n $SESSION_MANAGER ]] && pid="${SESSION_MANAGER##*/}"
[[ -n $UPSTART_SESSION ]] && pid="${UPSTART_SESSION##*/}"
process_name=$(cat /proc/$pid/cmdline)
pretty_name=$DESKTOP_SESSION
echo "$process_name : $pid : $pretty_name"
And output will be like that:
# Arch with xfce
xfce4-session : 3021 : xfce
# Ubuntu
/sbin/upstart--user : 3153 : ubuntu
# Xubuntu
init--user : 2343 : xubuntu
EDIT: Your method can work in some cases, but most of the time it will fail. Just because right now on ubuntu I have:
$ ls -1 /usr/share/xsessions/
openbox.desktop
ubuntu.desktop
And x-session starting process in Unity looks like that:
root 964 0.0 0.0 276680 6032 ? SLsl 00:16 0:00 /usr/sbin/lightdm
root 997 3.8 0.9 255676 74708 tty7 Ss+ 00:16 0:15 \_ /usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
root 1196 0.0 0.0 230304 6420 ? Sl 00:16 0:00 \_ lightdm --session-child 12 19
user 1442 0.0 0.0 53756 4924 ? Ss 00:16 0:00 \_ /sbin/upstart --user
user 1734 0.0 0.0 39992 280 ? S 00:16 0:00 \_ upstart-udev-bridge --daemon --user
user 1737 0.2 0.0 43932 4332 ? Ss 00:16 0:00 \_ dbus-daemon --fork --session --address=unix:abstract=/tmp/dbus-wkfpguwfxw
user 1749 0.0 0.1 93416 8756 ? Ss 00:16 0:00 \_ /usr/lib/x86_64-linux-gnu/hud/window-stack-bridge
So there is no correlation between name of session in /usr/share/xsessions/ and real process cmdline. So pgrep won't find anything in that cases.