gethrtime(3C)

NAME

gethrtime() — get high resolution time

SYNOPSIS

#include <time.h>

hrtime_t gethrtime(void);

DESCRIPTION

The gethrtime() function returns the current high-resolution real time. Time is expressed as nanoseconds since a certain time in the past. This API uses a fast light weight system call to get the nanoseconds from a certain time. It is not correlated in any way to the time of day. This API is used for performance measurement tasks and is used for cheap and accurate interval timing.

hrtime_t is a signed 64-bit number.

RETURN VALUE

Upon successful completion, gethrtime() returns a number of nanoseconds. Otherwise, a value of -1 is returned.

WARNINGS

This API will only be available if the application is being compiled in -Ae mode (extended ANSI) because 64-bit integer numbers are not available in -Aa (ANSI) mode. Please refer to cc(1).

EXAMPLES

The following code fragment measures the average cost of getgid():

hrtime_t begin, end;

int i, count = 1000;

begin = gethrtime();

for (i = 0; i < count; i++)

        getgid();

end = gethrtime();

printf("Avg getgid() time = %lld nsec", (end - begin)/count );