io_uring_prep_fixed_fd_install(3) — Linux manual page


io_uring_pr..._fd_install(3) liburing Manualio_uring_pr..._fd_install(3)

NAME         top

       io_uring_prep_fixed_fd_install - prepare fixed file fd
       installation request

SYNOPSIS         top

       #include <liburing.h>

       void io_uring_prep_fixed_fd_install(struct io_uring_sqe *sqe,
                                           int fd,
                                           unsigned int file_flags,
                                           unsigned int flags);

DESCRIPTION         top

       The io_uring_prep_fixed_fd_install(3) helper prepares a fixed
       file descriptor installation. The submission queue entry sqe is
       setup to install the direct/fixed file descriptor fd with the
       specified file_flags file installation flags, and the flags
       request specific flags into the normal process file table.

       One use case of direct/fixed file descriptors is to turn a
       regular file descriptor into a direct one, reducing the overhead
       of any request that needs to access this file. This helper
       provides a way to go the other way, turning a direct descriptor
       into a regular file descriptor that can then subsequently be used
       by regular system calls that take a normal file descriptor.  This
       can be handy if no regular file descriptor exists for this direct
       descriptor. Either because it was instantiated directly as a
       fixed descriptor, or because the regular file was closed with
       close(2) after being turned into a direct descriptor.

       Upon successful return of this request, both a normal and fixed
       file descriptor exists for the same file. Either one of them may
       be used to access the file.  Either one of them may be closed
       without affecting the other one.

       file_flags may be either zero, or set to O_CLOEXEC to indicate
       that the new regular file descriptor should be closed during
       exec. Setting this field to anything but those two values will
       result in the request being failed with -EINVAL in the CQE res

       flags is as-of yet unused and must be set to zero.

RETURN VALUE         top


ERRORS         top

       The CQE res field will contain the result of the operation, which
       in this case will be the value of the new regular file
       descriptor. In case of failure, a negative value is returned.

SEE ALSO         top

       io_uring_get_sqe(3), io_uring_submit(3),
       io_uring_register_files(3), io_uring_unregister_files(3),
       io_uring_prep_close_direct(3), io_uring_prep_openat_direct(3)

COLOPHON         top

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-19.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to

liburing-2.6                December 8, 2023io_uring_pr..._fd_install(3)

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