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io_setup(2) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON

io_setup(2)                System Calls Manual                io_setup(2)

NAME         top

       io_setup - create an asynchronous I/O context

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <linux/aio_abi.h>
       #include <sys/syscall.h>    /* Definition of SYS_* constants */
       #include <unistd.h>

       long syscall(SYS_io_setup, unsigned int n, aio_context_t *ctx_idp);

DESCRIPTION         top

       Note: you probably want to use the io_setup(3) wrapper function
       provided by libaio; see VERSIONS.

       The io_setup() system call creates an asynchronous I/O context
       suitable for concurrently processing n operations.  The ctx_idp
       argument must not point to an AIO context that already exists, and
       must be initialized to 0 prior to the call.  On successful
       creation of the AIO context, *ctx_idp is filled in with the
       resulting handle.

RETURN VALUE         top

       On success, io_setup() returns 0.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       EAGAIN The specified n exceeds the limit of available events, as
              defined in /proc/sys/fs/aio-max-nr (see proc_sys_fs(5)).

       EFAULT An invalid pointer is passed for ctx_idp.

       EINVAL *ctx_idp is not initialized to 0.

       EINVAL The specified n exceeds internal limits.  n should be
              greater than 0.

       ENOMEM Insufficient kernel resources are available.

       ENOSYS io_setup() is not implemented on this architecture.

VERSIONS         top

       libaio ⟨https://pagure.io/libaio⟩ provides a wrapper function with
       the same name, but different prototype and return value.  You
       probably want to use that wrapper.

STANDARDS         top

       Linux.

HISTORY         top

       Linux 2.5.

SEE ALSO         top

       io_cancel(2), io_destroy(2), io_getevents(2), io_submit(2),
       io_setup(3), aio(7)

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
       for this manual page, see
       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
       This page was obtained from the tarball man-pages-6.19.tar.gz
       fetched from
       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
       2026-09-09.  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-
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       improvements to the information in this COLOPHON (which is not
       part of the original manual page), send a mail to
       [email protected]

Linux man-pages 6.19            2026-04-11                    io_setup(2)

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Pages that refer to this page: fork(2),  io_cancel(2),  io_destroy(2),  io_getevents(2),  io_submit(2),  syscalls(2),  io_setup(3),  proc_sys_fs(5),  systemd.exec(5),  aio(7)

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