List all systemd timers script

Two examples of how to show all systemd timers running on the current system. Requires root access.

Explanation

Thanks to the Freenode #systemd IRC channel (users dreisner and damjan), I learned that systemd requires the user to run systemctl --user list-timers in order to print the running timers.

If an administrator of the system wants to sudo or su as another user in order to see the timers, then they need to set XDG_RUNTIME_DIR envrionment variable.

The code here automates this process and shows all the running timers.

Implementation

I first implemented the script using Haskell, but felt like the problem was a good fit for Bash. So, I implemented another script using bash.

The user output should be identical between the scripts. Both require the user running the script to be root.

Example

$ sudo ./list-all-systemd-timers.hs
[sudo] password for david:
System timers:
NEXT                         LEFT         LAST                         PASSED  UNIT             ACTIVATES
Sun 2016-10-02 22:34:40 EDT  38min left   Sat 2016-10-01 22:34:40 EDT  23h ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
Mon 2016-10-03 00:00:00 EDT  2h 3min left Sun 2016-10-02 00:01:40 EDT  21h ago logrotate.timer             logrotate.service
Mon 2016-10-03 00:00:00 EDT  2h 3min left Sun 2016-10-02 00:01:40 EDT  21h ago man-db.timer             man-db.service
Mon 2016-10-03 00:00:00 EDT  2h 3min left Sun 2016-10-02 00:01:40 EDT  21h ago shadow.timer             shadow.service

4 timers listed.
Pass --all to see loaded but inactive timers, too.

Timers for david:
0 timers listed.
Pass --all to see loaded but inactive timers, too.

Timers for tester:
0 timers listed.
Pass --all to see loaded but inactive timers, too.