curl -I --interface wlan-sta0 https://www.africau.edu/images/default/sample.pdf -O
curl: (45) Couldn't bind to 'wlan-sta0'
# Returns 1, showing it failed
Trying with a valid interface, but offline:
curl -I --interface en0 https://www.africau.edu/images/default/sample.pdf -O
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0curl: (6) Could not resolve host: www.africau.edu
# Returns 1, showing it failed
It seems robust enough if the curl from openwrt have the --interface feature. I can integrate some logic to correctly monitor this using https://healthchecks.io notifications.
Call down all the interfaces and call it up all again.
…or, create a hotplug script (docs/guide-user/base-system/hotplug#iface) that downloads the file and put the commands above in a cron. It depends on preference.