---
name: "nbd_aio_peek_command_completed"
section: "3"
platform: "linux"
package: "libnbd"
version: "1.24.4-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/nbd_aio_peek_command_completed"
---

# nbd\_aio\_peek\_command\_completed(3)

check if any command has completed

## NAME

nbd\_aio\_peek\_command\_completed - check if any command has completed

## SYNOPSIS

```
 #include <libnbd.h>
 int64_t nbd_aio_peek_command_completed (
           struct nbd_handle *h
         );
```

## DESCRIPTION

Return the unique positive 64 bit cookie of the first non-retired but completed command, `0` if there are in-flight commands but none of them are awaiting retirement, or `-1` on error including when there are no in-flight commands. Any cookie returned by this function must still be passed to [**nbd\_aio\_command\_completed**(3)](/nbd_aio_command_completed/3.md) to actually retire the command and learn whether the command was successful.

## RETURN VALUE

This call returns a 64 bit signed integer ≥ `0`.

## ERRORS

On error `-1` is returned.

Refer to "ERROR HANDLING" in [**libnbd**(3)](/libnbd/3.md) for how to get further details of the error.

The following parameters must not be NULL: `"h"`. For more information see "Non-NULL parameters" in [**libnbd**(3)](/libnbd/3.md).

## VERSION

This function first appeared in libnbd 1.0.

If you need to test if this function is available at compile time check if the following macro is defined:

```
 #define LIBNBD_HAVE_NBD_AIO_PEEK_COMMAND_COMPLETED 1
```

## SEE ALSO

[**nbd\_aio\_command\_completed**(3)](/nbd_aio_command_completed/3.md), [**nbd\_create**(3)](/nbd_create/3.md), [**libnbd**(3)](/libnbd/3.md).

## AUTHORS

Eric Blake

Richard W.M. Jones

## COPYRIGHT

Copyright Red Hat

## LICENSE

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA