io\_uring\_prep\_pipe(3) liburing Manual io\_uring\_prep\_pipe(3)

# [NAME](#NAME)

io\_uring\_prep\_pipe - prepare a pipe creation request

# [SYNOPSIS](#SYNOPSIS)

```
#include <liburing.h>
```

```
void io_uring_prep_pipe(struct io_uring_sqe *sqe,
                        int *fds,
                        int pipe_flags);

void io_uring_prep_pipe_direct(struct io_uring_sqe *sqe,
                               int *fds,
                               int pipe_flags,
                               unsigned int file_index);
```

```

```

# [DESCRIPTION](#DESCRIPTION)

The [**io\_uring\_prep\_pipe**(3)](/man/os/liburing/io_uring_prep_pipe.3) function prepares a pipe creation request. The submission queue entry *sqe* is setup to create a pipe with the created descriptors being copied to the array indicated by *fds* and using *pipe\_flags* as the pipe creation flags. See [**pipe2(2)**](/man/os/liburing/pipe2.2) for details on the flags accepted.

The [**io\_uring\_prep\_pipe\_direct**(3)](/man/os/liburing/io_uring_prep_pipe_direct.3) function works in the same way, however it uses fixed/registered file descriptors rather than normal file descriptors. This helper takes an additional *file\_index* argument, which can set to either an explicit direct descriptor offset to create the two pipe file descriptors at, or it can be set to **IORING\_FILE\_INDEX\_ALLOC** to let io\_uring pick any available descriptors for the read and write side of the pipe. If a specific index is given, the read side of the pipe will be created at that offset, if free, and the write side will be created at the next (+1) index. Both of these must be currently unused, or the operation will fail. Also see [**io\_uring\_prep\_accept\_direct**(3)](/man/os/liburing/io_uring_prep_accept_direct.3) or [**io\_uring\_prep\_socket\_direct**(3)](/man/os/liburing/io_uring_prep_socket_direct.3) for details on the *file\_index* parameter.

For both the direct and normal file descriptor pipe request, the resulting input/read side of the pipe will be stored in *fds\[0]* and the output/write side of the pipe will be stored in *fds\[1]* upon successful completion of this request.

This function prepares an async [**pipe2**(2)](/man/os/liburing/pipe2.2) request. See that man page for details.

# [RETURN VALUE](#RETURN_VALUE)

None

# [ERRORS](#ERRORS)

The CQE *res* field will contain the result of the operation. See the related man page for details on possible values. Note that where synchronous system calls will return **-1** on failure and set *errno* to the actual error value, io\_uring never uses *errno*. Instead it returns the negated *errno* directly in the CQE *res* field.

# [SEE ALSO](#SEE_ALSO)

[**io\_uring\_get\_sqe**(3)](/man/os/liburing/io_uring_get_sqe.3), [**io\_uring\_submit**(3)](/man/os/liburing/io_uring_submit.3), [**pipe2**(2)](/man/os/liburing/pipe2.2), [**io\_uring\_prep\_accept\_direct**(3)](/man/os/liburing/io_uring_prep_accept_direct.3), [**io\_uring\_prep\_socket\_direct**(3)](/man/os/liburing/io_uring_prep_socket_direct.3)

April 8, 2025 liburing-2.10

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Document: io_uring_prep_pipe(3) from liburing 2.15-r5 (Chainguard OS)
Source: https://github.com/axboe/liburing.git