NAME
aioread - asynchronous read SYNOPSIS
#include
int aioread(struct aiocb *aiocbp); Link with -lrt. DESCRIPTION The aioread() function queues the I/O request described by the buffer pointed to by aiocbp. This function is the asynchronous analog of read(2). The arguments of the call read(fd, buf, count) correspond (in order) to the fields aiofildes, aiobuf, and aionbytes of the structure pointed to by aiocbp. (See aio(7) for a description of the aiocb structure.)
The data is read starting at the absolute file offset aiocbp->aiooff‐ set, regardless of the current file offset. After the call, the value of the current file offset is unspecified. The "asynchronous" means that this call returns as soon as the request has been enqueued; the read may or may not have completed when the call returns. One tests for completion using aioerror(3). The return sta‐ tus of a completed I/O operation can be obtained by aioreturn(3). Asynchronous notification of I/O completion can be obtained by setting
aiocbp->aiosigevent appropriately; see sigevent(7) for details. If POSIXPRIORITIZEDIO is defined, and this file supports it, then the asynchronous operation is submitted at a priority equal to that of
the calling process minus aiocbp->aioreqprio.
The field aiocbp->aiolioopcode is ignored. No data is read from a regular file beyond its maximum offset. RETURN VALUE
On success, 0 is returned. On error the request is not enqueued, -1 is returned, and errno is set appropriately. If an error is detected only
later, it will be reported via aioreturn(3) (returns status -1) and aioerror(3) (error status—whatever one would have gotten in errno, such as EBADF). ERRORS EAGAIN Out of resources. EBADF aiofildes is not a valid file descriptor open for reading. EINVAL One or more of aiooffset, aioreqprio, or aionbytes are invalid. ENOSYS aioread() is not implemented. EOVERFLOW
The file is a regular file, we start reading before end-of-file and want at least one byte, but the starting position is past the maximum offset for this file. VERSIONS The aioread() function is available since glibc 2.1. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌───────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├───────────┼───────────────┼─────────┤
│aioread() │ Thread safety │ MT-Safe │ └───────────┴───────────────┴─────────┘ CONFORMING TO
POSIX.1-2001, POSIX.1-2008. NOTES It is a good idea to zero out the control block before use. The con‐ trol block must not be changed while the read operation is in progress. The buffer area being read into must not be accessed during the opera‐ tion or undefined results may occur. The memory areas involved must remain valid. Simultaneous I/O operations specifying the same aiocb structure produce undefined results. EXAMPLE See aio(7). SEE ALSO aiocancel(3), aioerror(3), aiofsync(3), aioreturn(3), aiosus‐ pend(3), aiowrite(3), liolistio(3), aio(7) COLOPHON
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2012-05-08 AIOREAD(3)