Problem: missing check file open limit

[leejw51crypto]

in main, check current file open limit of the process.
if it's not enough

1. display how to increase
2. exit the program

[yihuang]

It's hard to decide on a minimum requirement though, the database is growing, and network connections also use file descriptors.

[leejw51crypto]

yes, getting minimum is difficult.
how about checking with the maximum?
for linux: unlimited
for mac: maximum file open limit, which system allow
for windows: need to check