# zx_vmo_read

## NAME

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vmo_read - read bytes from the VMO

## SYNOPSIS

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

zx_status_t zx_vmo_read(zx_handle_t handle,
                        void* buffer,
                        uint64_t offset,
                        size_t buffer_size);
```

## DESCRIPTION

`zx_vmo_read()` attempts to read exactly *buffer_size* bytes from a VMO at *offset*.

*buffer* pointer to a user buffer to read bytes into.

*buffer_size* number of bytes to attempt to read. *buffer* buffer should be large
enough for at least this many bytes.

## RIGHTS

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*handle* must be of type **ZX_OBJ_TYPE_VMO** and have **ZX_RIGHT_READ**.

## RETURN VALUE

`zx_vmo_read()` returns **ZX_OK** on success, and exactly *buffer_size* bytes will
have been written to *buffer*.
In the event of failure, a negative error value is returned, and the number of
bytes written to *buffer* is undefined.

## ERRORS

**ZX_ERR_BAD_HANDLE**  *handle* is not a valid handle.

**ZX_ERR_WRONG_TYPE**  *handle* is not a VMO handle.

**ZX_ERR_ACCESS_DENIED**  *handle* does not have the **ZX_RIGHT_READ** right.

**ZX_ERR_INVALID_ARGS**  *buffer* is an invalid pointer or NULL.

**ZX_ERR_OUT_OF_RANGE**  *offset* starts at or beyond the end of the VMO,
                         or VMO is shorter than *buffer_size*.

**ZX_ERR_BAD_STATE**  VMO has been marked uncached and is not directly readable.

## SEE ALSO

 - [`zx_vmo_clone()`]
 - [`zx_vmo_create()`]
 - [`zx_vmo_get_size()`]
 - [`zx_vmo_op_range()`]
 - [`zx_vmo_set_cache_policy()`]
 - [`zx_vmo_set_size()`]
 - [`zx_vmo_write()`]

<!-- References updated by update-docs-from-abigen, do not edit. -->

[`zx_vmo_clone()`]: vmo_clone.md
[`zx_vmo_create()`]: vmo_create.md
[`zx_vmo_get_size()`]: vmo_get_size.md
[`zx_vmo_op_range()`]: vmo_op_range.md
[`zx_vmo_set_cache_policy()`]: vmo_set_cache_policy.md
[`zx_vmo_set_size()`]: vmo_set_size.md
[`zx_vmo_write()`]: vmo_write.md