clock_gettime(3)					     Library Functions Manual						  clock_gettime(3)

clock_gettime, clock_settime - Obtains or sets the time for the specified clock (P1003.1b) LIBRARY
Realtime Library (, librt.a) SYNOPSIS
#include <time.h> int clock_gettime ( clockid_t clock_id, struct timespec *tp); int clock_settime ( clockid_t clock_id, const struct timespec *tp); PARAMETERS
clock_id The clock type used to obtain the time for the clock that is set. The CLOCK_REALTIME clock is supported and represents the TIME-OF-DAY clock for the system. *tp A pointer to a timespec data structure. DESCRIPTION
The clock_gettime function returns the current time (in seconds and nanoseconds) for the specified clock. The clock_settime function sets the specified clock. The CLOCK_REALTIME clock measures the amount of time elapsed since 00:00:00:00 January 1, 1970 Greenwich Mean Time (GMT), otherwise known as the Epoch. Time values that fall between two non-negative integer multiples of the resolution are truncated down to the smaller multiple of the resolution. You must have superuser privileges to use the clock_settime function. RETURN VALUES
On a successful call to the clock_gettime or clock_settime functions, a value of 0 (zero) is returned. On an unsuccessful call, a value of -1 is returned and errno is set to indicate that an error occurred. ERRORS
The clock_gettime and clock_settime functions fail under the following conditions: [EINVAL] The clock_id argument does not specify a known clock. The value pointed to by the tp argument to the clock_settime function is outside the range for the given clock_id. The tp argument specified a nanosecond value less than zero or greater than or equal to 1000 million. [EPERM] The requesting process does not have the appropriate privilege to set the specified clock. RELATED INFORMATION
Functions: time(1), clock_getres(3), ctime(3), timer_gettime(3) Guide to Realtime Programming delim off clock_gettime(3)

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