MICROTIME(9)

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

# NAME

`bintime`, `getbintime`, `microtime`, `getmicrotime`, `nanotime`, `getnanotime` — get the current time

# SYNOPSIS

`#include <sys/time.h>`

void
`bintime`(struct bintime *bt);

void
`getbintime`(struct bintime *bt);

void
`microtime`(struct timeval *tv);

void
`getmicrotime`(struct timeval *tv);

void
`nanotime`(struct timespec *tsp);

void
`getnanotime`(struct timespec *tsp);

# DESCRIPTION

The `bintime`() and `getbintime`() functions store the system time as a struct bintime at the addresses specified by bt. The `microtime`() and `getmicrotime`() functions perform the same utility, but record the time as a struct timeval instead. Similarly the `nanotime`() and `getnanotime`() functions store the time as a struct timespec. The structures are described in timeval(3).

The `bintime`(), `microtime`(), and `nanotime`() functions always query the timecounter to return the current time as precisely as possible. Whereas `getbintime`(), `getmicrotime`(), and `getnanotime`() functions are abstractions which return a less precise, but faster to obtain, time.

The intent of the `getbintime`(), `getmicrotime`(), and `getnanotime`() functions is to enforce the user's preference for timer accuracy versus execution time. They should be used where a precision of 1/HZ (e.g., 10 msec on a 100HZ machine, see hz(9)) is acceptable or where performance is priority.

The system realtime clock is guaranteed to be monotonically increasing at all times. As such, all calls to these functions are guaranteed to return a system time greater than or equal to the system time returned in any previous calls. Comparable functions exist to retrieve the time elapsed since boot; see microuptime(9).

# CODE REFERENCES

The implementation of the `microtime`() family of functions is in sys/kern/kern_tc.c as a part of the timecounter(9) framework.

The implementation of the time counter sources used by the timecounter(9) is machine dependent, hence its location in the source code tree varies from architecture to architecture.

# SEE ALSO

settimeofday(2), bintime_add(9), inittodr(9), time_second(9), tvtohz(9)

# AUTHORS

This manual page was written by Jeremy Cooper and
Kelly Yancey <kbyanc@posi.net>.

# CAVEATS

Despite the guarantee that the system realtime clock will always be monotonically increasing, it is always possible for the system clock to be manually reset by the system administrator to any date.

May 13, 2013 | NetBSD 11.0