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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | SEE ALSO | COLOPHON |
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io_uring_prep_read(3) liburing Manual io_uring_prep_read(3)
io_uring_prep_read - prepare I/O read request
#include <liburing.h>
void io_uring_prep_read(struct io_uring_sqe *sqe,
int fd,
void *buf,
unsigned nbytes,
__u64 offset);
The io_uring_prep_read(3) prepares an IO read request. The
submission queue entry sqe is setup to use the file descriptor fd
to start reading nbytes into the buffer buf at the specified
offset.
On files that support seeking, if the offset is set to -1, the
read operation commences at the file offset, and the file offset
is incremented by the number of bytes read. See read(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 must be 0 or
-1.
After the read has been prepared it can be submitted with one of
the submit functions.
None
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.
io_uring_get_sqe(3), io_uring_prep_readv(3),
io_uring_prep_readv2(3), io_uring_submit(3)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-02.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
liburing-2.1 November 15, 2021 io_uring_prep_read(3)
Pages that refer to this page: io_uring_get_sqe(3), io_uring_prep_read(3), io_uring_prep_read_fixed(3), io_uring_prep_read_multishot(3), io_uring_prep_readv2(3), io_uring_prep_readv(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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