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

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

Note:  this  page describes the raw Linux system call interface.  The wrapper function provided by libaio
       uses a different type for the ctx_id argument.  See VERSIONS.

       The io_getevents() system call attempts to read at least min_nr events and  up  to  nr  events  from  the
       completion queue of the AIO context specified by ctx_id.

       The  timeout  argument  specifies  the  amount of time to wait for events, and is specified as a relative
       timeout in a timespec(3) structure.

       The specified time will be rounded up to the system clock granularity and is  guaranteed  not  to  expire
       early.

       Specifying timeout as NULL means block indefinitely until at least min_nr events have been obtained.

EFAULT Either events or timeout is an invalid pointer.

       EINTR  Interrupted by a signal handler; see signal(7).

       EINVALctx_id is invalid.  min_nr is out of range or nr is out of range.

       ENOSYSio_getevents() is not implemented on this architecture.

       Linux 2.5.

       Standard C library (libc, -lc)

       Alternatively, Asynchronous I/O library (libaio, -laio); see VERSIONS.

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

       On  success,  io_getevents()  returns  the  number  of  events read.  This may be 0, or a value less than
       min_nr, if the timeout expired.  It may also be a nonzero  value  less  than  min_nr,  if  the  call  was
       interrupted by a signal handler.

       For the failure return, see VERSIONS.

io_cancel(2), io_destroy(2), io_setup(2), io_submit(2), timespec(3), aio(7), time(7)

Linux man-pages 6.9.1                              2024-05-02                                    io_getevents(2)

       Linux.

#include<linux/aio_abi.h>    /* Definition of *io_* types */
       #include<sys/syscall.h>      /* Definition of SYS_* constants */
       #include<unistd.h>intsyscall(SYS_io_getevents,aio_context_tctx_id,longmin_nr,longnr,structio_event*events,structtimespec*timeout);Note: glibc provides no wrapper for io_getevents(), necessitating the use of syscall(2).

       You probably want to use the io_getevents() wrapper function provided by libaio.

       Note that the libaio wrapper function uses a different type (io_context_t) for the ctx_id argument.  Note
       also  that  the  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 syscall(2), then the return value follows the usual conventions for indicating
       an error: -1, with errno set to a (positive) value that indicates the error.