I'm looking for a way to find out the open FD limit under Ubuntu machines which doesn't have the `/proc/PID/limits`

, namely EC2 machines.

I have been looking into `/proc/PID/limits`

, and found the the entry `FDSize`

with values like:

```
FDSize: 256
FDSize: 512
```

Any way I can deduce the maximum allowed open file descriptors from this value?