mirror of https://github.com/mkerrisk/man-pages
131 lines
3.4 KiB
Groff
131 lines
3.4 KiB
Groff
.\" Copyright (C) 2003 Free Software Foundation, Inc.
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.\"
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.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
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.\" This file is distributed according to the GNU General Public License.
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.\" %%%LICENSE_END
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.\"
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.TH IO_GETEVENTS 2 2020-06-09 "Linux" "Linux Programmer's Manual"
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.SH NAME
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io_getevents \- read asynchronous I/O events from the completion queue
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.SH SYNOPSIS
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.nf
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.BR "#include <linux/aio_abi.h>" " /* Defines needed types */"
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.BR "#include <linux/time.h>" " /* Defines 'struct timespec' */"
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.PP
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.BI "int io_getevents(io_context_t " ctx_id ", long " min_nr ", long " nr ,
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.BI " struct io_event *" events \
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", struct timespec *" timeout );
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.fi
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.PP
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.IR Note :
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There is no glibc wrapper for this system call; see NOTES.
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.SH DESCRIPTION
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The
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.BR io_getevents ()
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system call
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attempts to read at least \fImin_nr\fP events and
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up to \fInr\fP events from the completion queue of the AIO context
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specified by \fIctx_id\fP.
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.PP
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The \fItimeout\fP argument specifies the amount of time to wait for events,
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and is specified as a relative timeout in a structure of the following form:
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.PP
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.in +4n
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.EX
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struct timespec {
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time_t tv_sec; /* seconds */
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long tv_nsec; /* nanoseconds [0 .. 999999999] */
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};
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.EE
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.in
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.PP
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The specified time will be rounded up to the system clock granularity
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and is guaranteed not to expire early.
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.PP
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Specifying
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.I timeout
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as NULL means block indefinitely until at least
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.I min_nr
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events have been obtained.
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.SH RETURN VALUE
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On success,
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.BR io_getevents ()
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returns the number of events read.
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This may be 0, or a value less than
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.IR min_nr ,
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if the
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.I timeout
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expired.
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It may also be a nonzero value less than
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.IR min_nr ,
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if the call was interrupted by a signal handler.
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.PP
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For the failure return, see NOTES.
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.SH ERRORS
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.TP
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.B EFAULT
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Either \fIevents\fP or \fItimeout\fP is an invalid pointer.
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.TP
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.B EINTR
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Interrupted by a signal handler; see
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.BR signal (7).
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.TP
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.B EINVAL
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\fIctx_id\fP is invalid.
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\fImin_nr\fP is out of range or \fInr\fP is
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out of range.
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.TP
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.B ENOSYS
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.BR io_getevents ()
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is not implemented on this architecture.
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.SH VERSIONS
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The asynchronous I/O system calls first appeared in Linux 2.5.
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.SH CONFORMING TO
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.BR io_getevents ()
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is Linux-specific and should not be used in
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programs that are intended to be portable.
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.SH NOTES
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Glibc does not provide a wrapper function for this system call.
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You could invoke it using
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.BR syscall (2).
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But instead, you probably want to use the
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.BR io_getevents ()
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wrapper function provided by
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.\" http://git.fedorahosted.org/git/?p=libaio.git
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.IR libaio .
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.PP
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Note that the
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.I libaio
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wrapper function uses a different type
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.RI ( io_context_t )
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.\" But glibc is confused, since <libaio.h> uses 'io_context_t' to declare
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.\" the system call.
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for the
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.I ctx_id
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argument.
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Note also that the
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.I libaio
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wrapper does not follow the usual C library conventions for indicating errors:
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on error it returns a negated error number
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(the negative of one of the values listed in ERRORS).
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If the system call is invoked via
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.BR syscall (2),
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then the return value follows the usual conventions for
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indicating an error: \-1, with
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.I errno
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set to a (positive) value that indicates the error.
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.SH BUGS
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An invalid
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.IR ctx_id
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may cause a segmentation fault instead of generating the error
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.BR EINVAL .
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.SH SEE ALSO
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.BR io_cancel (2),
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.BR io_destroy (2),
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.BR io_setup (2),
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.BR io_submit (2),
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.BR aio (7),
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.BR time (7)
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.\" .SH AUTHOR
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.\" Kent Yoder.
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