Runuser bug?

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1

Hi
Am currently developing some bash system automation notification scripts and in the process I note a potential bug re command runuser? Please avice if I am dreaming?

Running

$ uname -a
Linux earth 6.8.9-200.fc39.x86_64 #1 SMP PREEMPT_DYNAMIC Thu May 2 18:44:19 UTC 2024 x86_64 GNU/Linux

Note also that clamupdate is in visudo:
clamupdate earth= NOPASSWD: /usr/bin/notify-send, /usr/local/bin/notify-send-all

where for notify-send-all refer to notify-send-all

In adapting the script re send-to where clamupdate(by freshclam process) would send notify-send to display :X of relevant user

So during testing I noted:

[root@earth:]# runuser -u clamupdate – /usr/bin/whoami
clamupdate

[root@earth:]# runuser -u clamupdate – /usr/bin/echo $(/usr/bin/whoami)
root
[root@earth:]# runuser -u clamupdate – /usr/bin/echo $(runuser -u clamupdate – /usr/bin/whoami)
clamupdate

While no bash superexpert, It would appear to me that for both cases the answer should be clamupdate or any other -u username?

If the different answer is right, could someone please explain why?

2

In

runuser -u clamupdate – /usr/bin/echo $(/usr/bin/whoami)

the subexpression $(/usr/bin/whoami) gets evaluated before clamupdate is run, thus it would be equivalent to running

runuser -u clamupdate – /usr/bin/echo root

You can run set -x before running any of the commands to see what is actually happening.

1 Like
3

Thank you - understood.