How can I get system time from a proc file?

How can I get system time from a proc file? I know we can get system time from some commands such as date, and also can write some code based on time API. But I really need to use a simple proc file to get the time. No matter what the time format is, a simple value is OK. For example, the total seconds from 1970/1/1 is really good enough.开发者_JAVA技巧

Yes, you can :

cat /proc/driver/rtc

From man:

RTC vs system clock
   RTCs should not be confused with the system clock, which is a
   software clock maintained by the kernel and used to implement
   gettimeofday(2) and time(2), as well as setting timestamps on files,
   and so on.  The system clock reports seconds and microseconds since a
   start point, defined to be the POSIX Epoch: 1970-01-01 00:00:00 +0000
   (UTC).

More here

You can get the amount of time since the system booted from /proc/uptime, but there is no way I know of to get the real time from /proc.