time

• #include <posix/time.h>;

• Defines APIs related to timers

[中文]

Header File

• time.h

Functions

clock_t clock(void)

Report CPU time used.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock.html

Note

This function does NOT report the number of ticks spent by the calling thread.

Returns

The number of FreeRTOS ticks since the scheduler was started minus the ticks spent in the idle task.

int clock_getcpuclockid(pid_t pid, clockid_t *clock_id)

Access a process CPU-time clock.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getcpuclockid.html

Note

This function is currently unsupported.

Return values

EPERM –

int clock_getres(clockid_t clock_id, struct timespec *res)

Returns the resolution of a clock.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html

Note

clock_id is ignored

This function stores the resolution of the FreeRTOS tick count in the object res points to.

Return values

0 – - Upon successful execution

int clock_gettime(clockid_t clock_id, struct timespec *tp)

Returns the current value for the specified clock, clock_id.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_gettime.html

Note

clock_id is ignored

this function does not check for overflows of time_t.

Return values

0 – - Upon successful completion.

int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *rqtp, struct timespec *rmtp)

High resolution sleep with specifiable clock.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_nanosleep.html

Note

clock_id is ignored, as this function uses the FreeRTOS tick count as its clock.

flags is ignored, if INCLUDE_vTaskDelayUntil is 0. i.e. the FreeRTOS function vTaskDelayUntil isn’t available.

rmtp is also ignored, as signals are not implemented.

Return values

• 0 – - Upon successful completion.

• EINVAL – - The rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.

int clock_settime(clockid_t clock_id, const struct timespec *tp)

Sets the time for the specified clock.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_settime.html

Note

This function is currently unsupported, as FreeRTOS does not provide a function to modify the tick count.

Return values

-1 – with errno set to EPERM.

int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)

High resolution sleep.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/nanosleep.html

Note

rmtp is ignored, as signals are not implemented.

Return values

• 0 – - Upon successful completion.

• -1 – - The rqtp argument is invalid OR the rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.

int timer_create(clockid_t clockid, struct sigevent *evp, timer_t *timerid)

Create a per-process timer.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html

Possible errno values

ENOTSUP - If evp is NULL OR evp->sigen_notify == SIGEV_SIGNAL.

EAGAIN - The system lacks sufficient signal queuing resources to honor the request.

Note

clock_id is ignored, as this function used the FreeRTOS tick count as its clock.

evp.sigev_notify must be set to SIGEV_THREAD, since signals are currently not supported.

Return values

• 0 – - Upon successful completion, with location referenced by timerid updated.

• -1 – - If an error occurs. errno is also set.

int timer_delete(timer_t timerid)

Delete a per-process timer.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html

Return values

0 – - Upon successful completion.

int timer_getoverrun(timer_t timerid)

Get the timer overrun count.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html

Return values

0 – - Always return 0, since signals are not supported.

int timer_gettime(timer_t timerid, struct itimerspec *value)

Get the amount of time until the timer expires.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_gettime.html

Return values

0 – - Upon successful completion.

int timer_settime(timer_t timerid, int flags, const struct itimerspec *value, struct itimerspec *ovalue)

Set the time until the next expiration of the timer.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_settime.html

Possible errno values

EINVAL - A value structure specified a nanosecond value less than zero or greater than or equal to 1000 million, AND the it_value member of that structure did not specify zero seconds and nanoseconds.

Return values

• 0 – - Upon successful completion.

• -1 – - An error occurred, errno is also set.

Structures

struct timespec

represents an elapsed time

Public Members

time_t tv_sec

Seconds.

long tv_nsec

Nanoseconds.

struct itimerspec

timer

Public Members

struct timespec it_interval

Timer period.

struct timespec it_value

Timer expiration.

Macros

MICROSECONDS_PER_SECOND

Microseconds per second.

NANOSECONDS_PER_SECOND

Nanoseconds per second.

NANOSECONDS_PER_TICK

Nanoseconds per FreeRTOS tick.

CLOCK_REALTIME

The identifier of the system-wide clock measuring real time.

CLOCK_MONOTONIC

The identifier for the system-wide monotonic clock.

CLOCKS_PER_SEC

TIMER_ABSTIME