io_getevents(2)

1IO_GETEVENTS(2)            Linux Programmer's Manual           IO_GETEVENTS(2)
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NAME

6       io_getevents - read asynchronous I/O events from the completion queue
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SYNOPSIS

9       #include <linux/aio_abi.h>         /* Defines needed types */
10       #include <linux/time.h>            /* Defines 'struct timespec' */
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12       int io_getevents(aio_context_t ctx_id, long min_nr, long nr,
13                        struct io_event *events, struct timespec *timeout);
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15       Note: There is no glibc wrapper for this system call; see NOTES.
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DESCRIPTION

18       Note:  this  page  describes  the raw Linux system call interface.  The
19       wrapper function provided by libaio  uses  a  different  type  for  the
20       ctx_id argument.  See NOTES.
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22       The  io_getevents() system call attempts to read at least min_nr events
23       and up to nr events from the completion queue of the AIO context speci‐
24       fied by ctx_id.
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26       The  timeout  argument specifies the amount of time to wait for events,
27       and is specified as a relative timeout in a structure of the  following
28       form:
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30           struct timespec {
31               time_t tv_sec;      /* seconds */
32               long   tv_nsec;     /* nanoseconds [0 .. 999999999] */
33           };
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35       The  specified  time will be rounded up to the system clock granularity
36       and is guaranteed not to expire early.
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38       Specifying timeout as NULL means  block  indefinitely  until  at  least
39       min_nr events have been obtained.
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RETURN VALUE

42       On success, io_getevents() returns the number of events read.  This may
43       be 0, or a value less than min_nr, if the timeout expired.  It may also
44       be  a  nonzero value less than min_nr, if the call was interrupted by a
45       signal handler.
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47       For the failure return, see NOTES.
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ERRORS

50       EFAULT Either events or timeout is an invalid pointer.
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52       EINTR  Interrupted by a signal handler; see signal(7).
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54       EINVAL ctx_id is invalid.  min_nr is out of  range  or  nr  is  out  of
55              range.
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57       ENOSYS io_getevents() is not implemented on this architecture.
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VERSIONS

60       The asynchronous I/O system calls first appeared in Linux 2.5.
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CONFORMING TO

63       io_getevents()  is  Linux-specific  and  should not be used in programs
64       that are intended to be portable.
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NOTES

67       Glibc does not provide a wrapper function for this  system  call.   You
68       could  invoke  it  using syscall(2).  But instead, you probably want to
69       use the io_getevents() wrapper function provided by libaio.
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71       Note that the libaio wrapper function uses a  different  type  (io_con‐
72       text_t)  for  the  ctx_id  argument.  Note also that the libaio wrapper
73       does not follow the usual C library conventions for indicating  errors:
74       on  error it returns a negated error number (the negative of one of the
75       values  listed  in  ERRORS).   If  the  system  call  is  invoked   via
76       syscall(2), then the return value follows the usual conventions for in‐
77       dicating an error: -1, with errno set to a (positive) value that  indi‐
78       cates the error.
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BUGS

81       An  invalid ctx_id may cause a segmentation fault instead of generating
82       the error EINVAL.
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COLOPHON

88       This page is part of release 5.10 of the Linux  man-pages  project.   A
89       description  of  the project, information about reporting bugs, and the
90       latest    version    of    this    page,    can     be     found     at
91       https://www.kernel.org/doc/man-pages/.
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95Linux                             2020-12-21                   IO_GETEVENTS(2)