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# zx_object_wait_many
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Wait for signals on multiple objects.
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#include <zircon/syscalls.h>
zx_status_t zx_object_wait_many(zx_wait_item_t* items,
size_t num_items,
zx_time_t deadline);
`zx_object_wait_many()` is a blocking syscall which causes the caller to wait
until either the *deadline* passes or at least one object referred to in
*items* has a specified [signal][signals] asserted. If an object is already
asserting at least one of the specified signals, the wait ends immediately with
typedef struct {
zx_handle_t handle;
zx_signals_t waitfor;
zx_signals_t pending;
} zx_wait_item_t;
The caller must provide *count* `zx_wait_item_t`s in the *items* array,
containing the handle and signals bitmask to wait for for each item.
Each item should contain a valid *handle* referring to an object to
wait for, and a bitmask *waitfor* indicating which signals should wake
the calling thread.
The *deadline* parameter specifies a deadline with respect to
**ZX_CLOCK_MONOTONIC** and will be automatically adjusted according to the job's
[timer slack] policy. **ZX_TIME_INFINITE** is a special value meaning wait
Upon return, the *pending* field of *items* is filled with bitmaps indicating
which signals are pending for each item.
The maximum number of items that may be waited upon is **ZX_WAIT_MANY_MAX_ITEMS**,
which is 64. To wait on more objects at once use [Ports](/docs/reference/kernel_objects/
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Every entry of *items* must have a *handle* field with **ZX_RIGHT_WAIT**.
`zx_object_wait_many()` returns **ZX_OK** if any of *waitfor* signals were
active when the call was made, or observed on their respective object before
*deadline* passed.
In the event of **ZX_ERR_TIMED_OUT**, *items* may reflect state changes
that occurred after the deadline passed, but before the syscall returned.
In the event of **ZX_ERR_CANCELED**, one or more of the items being waited
upon have had their handles closed, and the *pending* field for those items
will have the **ZX_SIGNAL_HANDLE_CLOSED** bit set.
For any other return value, the *pending* fields of *items* are undefined.
**ZX_ERR_INVALID_ARGS** *items* isn't a valid pointer.
**ZX_ERR_OUT_OF_RANGE** *count* is greater than **ZX_WAIT_MANY_MAX_ITEMS**.
**ZX_ERR_BAD_HANDLE** one of *items* contains an invalid handle.
**ZX_ERR_ACCESS_DENIED** One or more of the provided *handles* does not
have **ZX_RIGHT_WAIT** and may not be waited upon.
**ZX_ERR_CANCELED** One or more of the provided *handles* was invalidated
(e.g., closed) during the wait.
**ZX_ERR_TIMED_OUT** The specified deadline passed before any of the specified signals are
observed on any of the specified handles.
**ZX_ERR_NOT_SUPPORTED** One of the *items* contains a handle that cannot
be waited one (for example, a Port handle).
**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.
*pending* more properly should be called *observed*.
See [signals] for more information about signals and their terminology.
- [timer slack](/docs/concepts/kernel/
- [`zx_object_wait_async()`]
- [`zx_object_wait_one()`]
[signals]: /docs/concepts/kernel/
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