When trying to monitor Linux procfs files, there is no error message, but effectively it does not work, because procfs files have a stat size of zero typically. For example:
> ll /proc/sys/kernel/random/boot_id -r--r--r-- 1 root root 0 Jul 4 16:45 /proc/sys/kernel/random/boot_id
So the actual contents is never inspected. For the example above there is content, however:
> wc /proc/sys/kernel/random/boot_id 1 1 37 /proc/sys/kernel/random/boot_id
So it would be nice to monitor such files for changes (for example).