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[man-pages.git] / man3 / lio_listio.3

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.TH LIO_LISTIO  3 2021-03-22  "" "Linux Programmer's Manual"
.SH NAME
lio_listio \- initiate a list of I/O requests
.SH SYNOPSIS
.nf
.B "#include <aio.h>"
.PP
.BI "int lio_listio(int " mode ", struct aiocb *restrict const " aiocb_list [restrict],
.BI "               int " nitems ", struct sigevent *restrict " sevp );
.PP
Link with \fI\-lrt\fP.
.fi
.SH DESCRIPTION
The
.BR lio_listio ()
function initiates the list of I/O operations described by the array
.IR aiocb_list .
.PP
The
.I mode
operation has one of the following values:
.TP
.B LIO_WAIT
The call blocks until all operations are complete.
The
.I sevp
argument is ignored.
.TP
.B LIO_NOWAIT
The I/O operations are queued for processing and the call returns immediately.
When all of the I/O operations complete, asynchronous notification occurs,
as specified by the
.IR sevp
argument; see
.BR sigevent (7)
for details.
If
.IR sevp
is NULL, no asynchronous notification occurs.
.PP
The
.I aiocb_list
argument is an array of pointers to
.I aiocb
structures that describe I/O operations.
These operations are executed in an unspecified order.
The
.I nitems
argument specifies the size of the array
.IR aiocb_list .
Null pointers in
.I aiocb_list
are ignored.
.PP
In each control block in
.IR aiocb_list ,
the
.I aio_lio_opcode
field specifies the I/O operation to be initiated, as follows:
.TP
.BR LIO_READ
Initiate a read operation.
The operation is queued as for a call to
.BR aio_read (3)
specifying this control block.
.TP
.BR LIO_WRITE
Initiate a write operation.
The operation is queued as for a call to
.BR aio_write (3)
specifying this control block.
.TP
.BR LIO_NOP
Ignore this control block.
.PP
The remaining fields in each control block have the same meanings as for
.BR aio_read (3)
and
.BR aio_write (3).
The
.I aio_sigevent
fields of each control block can be used to specify notifications
for the individual I/O operations (see
.BR sigevent (7)).
.SH RETURN VALUE
If
.I mode
is
.BR LIO_NOWAIT ,
.BR lio_listio ()
returns 0 if all I/O operations are successfully queued.
Otherwise, \-1 is returned, and
.I errno
is set to indicate the error.
.PP
If
.I mode
is
.BR LIO_WAIT ,
.BR lio_listio ()
returns 0 when all of the I/O operations have completed successfully.
Otherwise, \-1 is returned, and
.I errno
is set to indicate the error.
.PP
The return status from
.BR lio_listio ()
provides information only about the call itself,
not about the individual I/O operations.
One or more of the I/O operations may fail,
but this does not prevent other operations completing.
The status of individual I/O operations in
.IR aiocb_list
can be determined using
.BR aio_error (3).
When an operation has completed,
its return status can be obtained using
.BR aio_return (3).
Individual I/O operations can fail for the reasons described in
.BR aio_read (3)
and
.BR aio_write (3).
.SH ERRORS
The
.BR lio_listio ()
function may fail for the following reasons:
.TP
.B EAGAIN
Out of resources.
.TP
.B EAGAIN
.\" Doesn't happen in glibc(?)
The number of I/O operations specified by
.I nitems
would cause the limit
.BR AIO_MAX
to be exceeded.
.TP
.B EINTR
.I mode
was
.BR LIO_WAIT
and a signal
was caught before all I/O operations completed; see
.BR signal (7).
(This may even be one of the signals used for
asynchronous I/O completion notification.)
.TP
.B EINVAL
.I mode
is invalid, or
.\" Doesn't happen in glibc(?)
.I nitems
exceeds the limit
.BR AIO_LISTIO_MAX .
.TP
.B EIO
One of more of the operations specified by
.IR aiocb_list
failed.
.\" e.g., ioa_reqprio or aio_lio_opcode was invalid
The application can check the status of each operation using
.BR aio_return (3).
.PP
If
.BR lio_listio ()
fails with the error
.BR EAGAIN ,
.BR EINTR ,
or
.BR EIO ,
then some of the operations in
.IR aiocb_list
may have been initiated.
If
.BR lio_listio ()
fails for any other reason,
then none of the I/O operations has been initiated.
.SH VERSIONS
The
.BR lio_listio ()
function is available since glibc 2.1.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface       Attribute       Value
T{
.BR lio_listio ()
T}      Thread safety   MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
It is a good idea to zero out the control blocks before use.
The control blocks must not be changed while the I/O operations
are in progress.
The buffer areas being read into or written from
.\" or the control block of the operation
must not be accessed during the operations or undefined results may occur.
The memory areas involved must remain valid.
.PP
Simultaneous I/O operations specifying the same
.I aiocb
structure produce undefined results.
.SH SEE ALSO
.BR aio_cancel (3),
.BR aio_error (3),
.BR aio_fsync (3),
.BR aio_return (3),
.BR aio_suspend (3),
.BR aio_write (3),
.BR aio (7)