.\" Copyright 2003, Free Software Foundation, Inc.
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: GPL-1.0-or-later
.\"
.TH io_cancel 2 2026-04-11 "Linux man-pages 6.18"
.SH NAME
io_cancel \- cancel an outstanding asynchronous I/O operation
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/aio_abi.h>" "    /* Definition of needed types */"
.BR "#include <sys/syscall.h>" "      /* Definition of " SYS_* " constants */"
.B #include <unistd.h>
.P
.BI "int syscall(SYS_io_cancel, aio_context_t " ctx_id ", struct iocb *" iocb ,
.BI "            struct io_event *" result );
.fi
.SH DESCRIPTION
.IR Note :
you probably want to use the
.BR io_getevents (3)
wrapper function provided by
.IR libaio ;
see VERSIONS.
.P
The
.BR io_cancel ()
system call
attempts to cancel an asynchronous I/O operation previously submitted with
.BR io_submit (2).
The
.I iocb
argument describes the operation to be canceled and the
.I ctx_id
argument is the AIO context to which the operation was submitted.
If the operation is successfully canceled, the event will be copied into
the memory pointed to by
.I result
without being placed into the
completion queue.
.SH RETURN VALUE
On success,
.BR io_cancel ()
returns 0.
On error,
\-1 is returned,
and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EAGAIN
The
.I iocb
specified was not canceled.
.TP
.B EFAULT
One of the data structures points to invalid data.
.TP
.B EINVAL
The AIO context specified by
.I ctx_id
is invalid.
.TP
.B ENOSYS
.BR io_cancel ()
is not implemented on this architecture.
.SH VERSIONS
.UR https://pagure.io/libaio
.I libaio
.UE
provides a wrapper function with the same name,
but different prototype and return value.
You probably want to use that wrapper.
.SH STANDARDS
Linux.
.SH HISTORY
Linux 2.5.
.SH SEE ALSO
.BR io_destroy (2),
.BR io_getevents (2),
.BR io_setup (2),
.BR io_submit (2),
.BR io_cancel (3),
.BR aio (7)
.\" .SH AUTHOR
.\" Kent Yoder.