Originální popis anglicky:
readv - read a vector
Návod, kniha: POSIX Programmer's Manual
#include <sys/uio.h>
ssize_t readv(int
fildes, const struct iovec
* iov, int
iovcnt);
The
readv() function shall be equivalent to
read(), except as
described below. The
readv() function shall place the input data into
the
iovcnt buffers specified by the members of the
iov array:
iov[0],
iov[1], ...,
iov[
iovcnt-1]. The
iovcnt argument is valid if greater than 0 and less than or equal to
{IOV_MAX}.
Each
iovec entry specifies the base address and length of an area in
memory where data should be placed. The
readv() function shall always
fill an area completely before proceeding to the next.
Upon successful completion,
readv() shall mark for update the
st_atime field of the file.
Refer to
read() .
Refer to
read() .
In addition, the
readv() function shall fail if:
- EINVAL
- The sum of the iov_len values in the iov
array overflowed an ssize_t.
The
readv() function may fail if:
- EINVAL
- The iovcnt argument was less than or equal to 0, or
greater than {IOV_MAX}.
The following sections are informative.
The following example reads data from the file associated with the file
descriptor
fd into the buffers specified by members of the
iov
array.
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
...
ssize_t bytes_read;
int fd;
char buf0[20];
char buf1[30];
char buf2[40];
int iovcnt;
struct iovec iov[3];
iov[0].iov_base = buf0;
iov[0].iov_len = sizeof(buf0);
iov[1].iov_base = buf1;
iov[1].iov_len = sizeof(buf1);
iov[2].iov_base = buf2;
iov[2].iov_len = sizeof(buf2);
...
iovcnt = sizeof(iov) / sizeof(struct iovec);
bytes_read = readv(fd, iov, iovcnt);
...
None.
Refer to
read() .
None.
read() ,
writev() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<sys/uio.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
