| .\" Copyright (C) 2021 Stefan Roesch <shr@fb.com> |
| .\" |
| .\" SPDX-License-Identifier: LGPL-2.0-or-later |
| .\" |
| .TH io_uring_prep_write 3 "November 15, 2021" "liburing-2.1" "liburing Manual" |
| .SH NAME |
| io_uring_prep_write \- prepare I/O write request |
| .SH SYNOPSIS |
| .nf |
| .B #include <liburing.h> |
| .PP |
| .BI "void io_uring_prep_write(struct io_uring_sqe *" sqe "," |
| .BI " int " fd "," |
| .BI " const void *" buf "," |
| .BI " unsigned " nbytes "," |
| .BI " __u64 " offset ");" |
| .fi |
| .SH DESCRIPTION |
| .PP |
| The |
| .BR io_uring_prep_write (3) |
| prepares an IO write request. The submission queue entry |
| .I sqe |
| is setup to use the file descriptor |
| .I fd |
| to start writing |
| .I nbytes |
| from the buffer |
| .I buf |
| at the specified |
| .IR offset . |
| |
| On files that support seeking, if the offset is set to |
| .BR -1 , |
| the write operation commences at the file offset, and the file offset is |
| incremented by the number of bytes written. See |
| .BR write (2) |
| for more details. Note that for an async API, reading and updating the |
| current file offset may result in unpredictable behavior, unless access |
| to the file is serialized. It is not encouraged to use this feature if it's |
| possible to provide the desired IO offset from the application or library. |
| |
| On files that are not capable of seeking, the offset is ignored. |
| |
| After the write has been prepared, it can be submitted with one of the submit |
| functions. |
| |
| .SH RETURN VALUE |
| None |
| .SH ERRORS |
| The CQE |
| .I 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 |
| .B -1 |
| on failure and set |
| .I errno |
| to the actual error value, io_uring never uses |
| .IR errno . |
| Instead it returns the negated |
| .I errno |
| directly in the CQE |
| .I res |
| field. |
| .SH SEE ALSO |
| .BR io_uring_get_sqe (3), |
| .BR io_uring_submit (3) |