docs/syscalls/vmo_read.md

# zx_vmo_read

## NAME

vmo_read - read bytes from the VMO

## SYNOPSIS

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

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

```

## DESCRIPTION

**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.

## 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

[vmo_create](vmo_create.md),
[vmo_clone](vmo_clone.md),
[vmo_write](vmo_write.md),
[vmo_get_size](vmo_get_size.md),
[vmo_set_size](vmo_set_size.md),
[vmo_op_range](vmo_op_range.md).
[vmo_set_cache_policy](vmo_set_cache_policy.md)