linux - how can i show the size of files in /proc? it should not be size zero

Question

from the following message, we know that there are two characters in file /proc/sys/net/ipv4/ip_forward, but why ls just showed this file is of size zero?

i know this is not a file on disk, but a file in the memory, so is there any command which i can see the real size of the files in /proc?

root@OpenWrt:/proc/sys/net/ipv4# cat ip_forward | wc -c
2
root@OpenWrt:/proc/sys/net/ipv4# ls -l ip_forward
-rw-r--r--    1 root     root            0 Sep  3 00:20 ip_forward
root@OpenWrt:/proc/sys/net/ipv4# pwd
/proc/sys/net/ipv4 

Answer 1

Those are not really files on disk (as you mention) but they are also not files in memory - the names in /proc correspond to calls into the running kernel in the operating system, and the contents are generated on the fly.

The system doesn't know how large the files would be without generating them, but if you read the "file" twice there's no guarantee you get the same data because the system may have changed.

You might be looking for the program sysctl -a instead.