.\" Copyright (C) 2003 Free Software Foundation, Inc. .\" .\" SPDX-License-Identifier: GPL-1.0-or-later .\" .TH io_getevents 2 2024-05-02 "Linux man-pages 6.9.1" .SH NAME io_getevents \- read asynchronous I/O events from the completion queue .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .P Alternatively, Asynchronous I/O library .RI ( libaio ", " \-laio ); see VERSIONS. .SH SYNOPSIS .nf .BR "#include " " /* Definition of " *io_* " types */" .BR "#include " " /* Definition of " SYS_* " constants */" .B #include .P .BI "int syscall(SYS_io_getevents, aio_context_t " ctx_id , .BI " long " min_nr ", long " nr ", struct io_event *" events , .BI " struct timespec *" timeout ); .fi .P .IR Note : glibc provides no wrapper for .BR io_getevents (), necessitating the use of .BR syscall (2). .SH DESCRIPTION .IR Note : this page describes the raw Linux system call interface. The wrapper function provided by .I libaio uses a different type for the .I ctx_id argument. See VERSIONS. .P The .BR io_getevents () system call attempts to read at least \fImin_nr\fP events and up to \fInr\fP events from the completion queue of the AIO context specified by \fIctx_id\fP. .P The \fItimeout\fP argument specifies the amount of time to wait for events, and is specified as a relative timeout in a .BR timespec (3) structure. .P The specified time will be rounded up to the system clock granularity and is guaranteed not to expire early. .P Specifying .I timeout as NULL means block indefinitely until at least .I min_nr events have been obtained. .SH RETURN VALUE On success, .BR io_getevents () returns the number of events read. This may be 0, or a value less than .IR min_nr , if the .I timeout expired. It may also be a nonzero value less than .IR min_nr , if the call was interrupted by a signal handler. .P For the failure return, see VERSIONS. .SH ERRORS .TP .B EFAULT Either \fIevents\fP or \fItimeout\fP is an invalid pointer. .TP .B EINTR Interrupted by a signal handler; see .BR signal (7). .TP .B EINVAL \fIctx_id\fP is invalid. \fImin_nr\fP is out of range or \fInr\fP is out of range. .TP .B ENOSYS .BR io_getevents () is not implemented on this architecture. .SH VERSIONS You probably want to use the .BR io_getevents () wrapper function provided by .\" http://git.fedorahosted.org/git/?p=libaio.git .IR libaio . .P Note that the .I libaio wrapper function uses a different type .RI ( io_context_t ) .\" But glibc is confused, since uses 'io_context_t' to declare .\" the system call. for the .I ctx_id argument. Note also that the .I libaio wrapper does not follow the usual C library conventions for indicating errors: on error it returns a negated error number (the negative of one of the values listed in ERRORS). If the system call is invoked via .BR syscall (2), then the return value follows the usual conventions for indicating an error: \-1, with .I errno set to a (positive) value that indicates the error. .SH STANDARDS Linux. .SH HISTORY Linux 2.5. .SH BUGS An invalid .I ctx_id may cause a segmentation fault instead of generating the error .BR EINVAL . .SH SEE ALSO .BR io_cancel (2), .BR io_destroy (2), .BR io_setup (2), .BR io_submit (2), .BR timespec (3), .BR aio (7), .BR time (7) .\" .SH AUTHOR .\" Kent Yoder.