main/syscalls/timer_create.md

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# zx_timer_create

## Summary

Create a timer.

## Declaration

```c
#include <zircon/syscalls.h>

zx_status_t zx_timer_create(uint32_t options,
                            zx_clock_t clock_id,
                            zx_handle_t* out);
```

## Description

`zx_timer_create()` creates a timer, an object that can signal
when a specified point in time has been reached. `clock_id` can
be either `ZX_CLOCK_MONOTONIC` or `ZX_CLOCK_BOOT`, depending on
which timeline the timer should use as its reference. Note that
timers on the boot timeline will elapse during suspend-to-idle,
but will not wake the system.

The *options* value specifies the coalescing behavior, which
controls whether the system can fire the time earlier or later
depending on other pending timers.

The possible values are:

+ `ZX_TIMER_SLACK_CENTER`
+ `ZX_TIMER_SLACK_EARLY`
+ `ZX_TIMER_SLACK_LATE`

Passing 0 in options is equivalent to `ZX_TIMER_SLACK_CENTER`.

See [timer slack](/docs/concepts/kernel/timer_slack.md) for more information.

The returned handle has the `ZX_RIGHT_DUPLICATE`, `ZX_RIGHT_TRANSFER`,
`ZX_RIGHT_WRITE`, `ZX_RIGHT_SIGNAL`, `ZX_RIGHT_WAIT`, and
`ZX_RIGHT_INSPECT` rights.

## Rights

Caller job policy must allow `ZX_POL_NEW_TIMER`.

## Return value

`zx_timer_create()` returns `ZX_OK` on success. In the event
of failure, a negative error value is returned.

## Errors

`ZX_ERR_INVALID_ARGS`  *out* is an invalid pointer or NULL or
*options* is not one of the `ZX_TIMER_SLACK` values or *clock_id* is
any value other than `ZX_CLOCK_MONOTONIC`.

`ZX_ERR_NO_MEMORY`  Failure due to lack of memory.
There is no good way for userspace to handle this (unlikely) error.
In a future build this error will no longer occur.

## See also

 - [`zx_deadline_after()`]
 - [`zx_handle_close()`]
 - [`zx_timer_cancel()`]
 - [`zx_timer_set()`]

[`zx_deadline_after()`]: deadline_after.md
[`zx_handle_close()`]: handle_close.md
[`zx_timer_cancel()`]: timer_cancel.md
[`zx_timer_set()`]: timer_set.md