Re: notify-send script messed up my environment

[Esteban L <esteban@little-beak.com>]

Thanks Mr. Ritter for sharing your expertise.

I think the one thing that kind of mystifies me a little is the bus
pipe. I am not familiar with that. A simple logout and log back in made
my "environment" return to "normal."

As you recommended, I simply ran the bash script on it's own. It worked
fine. But, as I was debugging it, over time, it stopped working.
Perhaps based, as you say, on nautilus getting confused.

It frustrated me a bit. Because, at that point, not even running the
script, alone, would work.

I found a better solution. I found a python API that was coded
specifically for this purpose, and I am more familiar with python than
I am with Bash (though I admit, Bash probably is better suited for many
tasks at this level). What's the saying about the "devil you know?" =)

Thanks again!


-----Original Message-----
From: Dan Ritter <dsr@randomstring.org>
To: Esteban L <esteban@little-beak.com>
Cc: debian-user <debian-user@lists.debian.org>
Subject: Re: notify-send script messed up my environment
Date: Tue, 7 May 2019 18:12:01 -0400

Esteban L wrote: 
> I stepped in poo, and broke a cardinal sin, trying a script that I
> didn't 100% understand. Now my environment is a little bit jacked.
> Not
> bad, still generally functioning. 
> 
> I was trying to get notifications to run from the command line,
> namely
> crontab. No easy task, at least, not as easy as I would have thought.
> 
> I created and ran this script I found online:
> #!/bin/bash
> username=$(/usr/bin/whoami)
> pid=$(pgrep -u $username nautilus)
> dbus=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ | sed
> 's/DBUS_SESSION_BUS_ADDRESS=//' )
> export DBUS_SESSION_BUS_ADDRESS=$dbus
> /usr/bin/notify-send "$(today)"
> 
> It seemed simple enough.
> 
> It even worked a few half dozen times. Until, it didn't.
> 
> I couldn't even run the script anymore, from the command line.
> I get the following error:
> grep: /proc/1700: Is a directory
> grep: 25836/environ: No such file or directory
> 
> I tried to "man" up but can't find anything on dbus, dbus_session
> etc.
> 
> I think it's as simple as messing up my environment.
> 
> Can someone throw me a bone? I guess I could restart, and I assume
> that
> should work, but that doesn't really explain to me why it broke,
> which
> interests me more.

Let's go through the script and see if we can explain it.

#!/bin/bash
    this is a bash script; please use /bin/bash to run it.
username=$(/usr/bin/whoami)
    run the command /usr/bin/whoami and put the output in the
    variable "username"
pid=$(pgrep -u $username nautilus)
    run pgrep, look for a process named nautilus owned by that
    username. Put the process ID in the variable "pid".
dbus=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$pid/environ | sed
's/DBUS_SESSION_BUS_ADDRESS=//' )
    look through the contents of the file in /proc/ (process id)
    /environ and find the line which contains the word
   DBUS_SESSION_BUS_ADDRESS. pipe that line through the stream
   editor to remove a bunch of characters and leave the rest.
   Put the value in the variable "dbus".
export DBUS_SESSION_BUS_ADDRESS=$dbus
    Make that "dbus" variable available to programs I run.
/usr/bin/notify-send "$(today)"
    Run "notify-send" with a value that comes from a program
    called "today".


Here are my suggestions:

Test running 
    /usr/bin/notify-send "Boo!"
If you get a notification, it's working. If not, you have deeper
problems.

Test with echo.
    After each variable assignment, run
        echo $username
    or
        echo $pid
    and so forth, as appropriate, to see what values you are
    getting.

Spaces and linebreaks are important.

"Nautilus" is not a foolproof way of knowing which X session is
wanted.

$(today) probably doesn't do what you want.

-dsr-