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## nng_aio_set_iov
set scatter/gather vector
### Synopsis
```c
#include <nng/nng.h>
int nng_aio_set_iov(nng_aio *aio, unsigned int niov, nng_iov *iov);
```
### Description
The `nng_aio_set_iov` function sets a ((scatter/gather)) vector _iov_ on the handle _aio_.
The _iov_ is a pointer to an array of _niov_ xref:nng_iov.5.adoc[`nng_iov`] structures, which have the following definition:
```c
typedef struct nng_iov {
void * iov_buf;
size_t iov_len;
};
```
The _iov_ is copied into storage in the _aio_ itself, so that callers may use stack allocated `nng_iov` structures.
The values pointed to by the `iov_buf` members are *not* copied by this function though.
A maximum of four (4) `nng_iov` members may be supplied.
NOTE: Earlier versions of the library could accept longer scatter-gather lists.
However, no known consumers have ever needed a scatter-gather list longer than 4 vectors.
As a result, the implementation limit was reduced, and heap allocations which could fail were removed.
### Return Values
This function returns 0 on success, and non-zero otherwise.
### Errors
[horizontal]
`NNG_EINVAL`:: Value of specified _niov_ is too large.
### See Also
xref:nng_aio_count.adoc[nng_aio_count],
xref:nng_aio_result.adoc[nng_aio_result],
xref:nng_iov.5.adoc[nng_iov]
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