TIME_SECOND(9)

TIME_SECOND(9) | Kernel Developer's Manual | TIME_SECOND(9)

# NAME

`time_second`, `time_uptime`, `time_uptime32` — system time variables

# SYNOPSIS

`#include <sys/time.h>`

extern const time_t time_second;
extern const time_t time_uptime;
extern const uint32_t time_uptime32;

# DESCRIPTION

The time_second variable is the system's “wall clock”, giving the number of seconds since midnight (0 hour), January 1, 1970, (proleptic) UTC, minus the number of leap seconds. It is set at boot by inittodr(9), and is updated periodically via timecounter(9) framework, and also updated by the settimeofday(2) system call.

The time_uptime variable is a monotonically increasing system clock. It is set at boot, and is updated periodically. (It is not updated by settimeofday(2).)

The time_uptime32 variable is the low-order 32 bits of time_uptime, which is cheaper to read on 32-bit platforms.

You must only read the variables time_second, time_uptime, and time_uptime32; you may not write to them or take their addresses. They may be implemented as macros.

The bintime(9), getbintime(9), microtime(9), getmicrotime(9), nanotime(9), and getnanotime(9) functions can be used to get the current time more accurately and in an atomic manner.

Similarly, the binuptime(9), getbinuptime(9), microuptime(9), getmicrouptime(9), nanouptime(9), and getnanouptime(9) functions can be used to get the time elapsed since boot more accurately and in an atomic manner.

# SEE ALSO

clock_settime(2), ntp_adjtime(2), timespec(3), hardclock(9), hz(9)

July 16, 2023 | NetBSD 11.0