Originální popis anglicky:
readv, writev - read or write data into multiple buffers
Návod, kniha: Linux Programmer's Manual
#include <sys/uio.h>
ssize_t readv(int fd, const struct iovec *vector, int count);
ssize_t writev(int fd, const struct iovec *vector, int count);
The
readv() function reads
count blocks from the file associated
with the file descriptor
fd into the multiple buffers described by
vector.
The
writev() function writes at most
count blocks described by
vector to the file associated with the file descriptor
fd.
The pointer
vector points to a
struct iovec defined in
<sys/uio.h> as
struct iovec {
void *iov_base; /* Starting address */
size_t iov_len; /* Number of bytes */
};
Buffers are processed in the order specified.
The
readv() function works just like
read(2) except that multiple
buffers are filled.
The
writev() function works just like
write(2) except that
multiple buffers are written out.
On success, the
readv() function returns the number of bytes read; the
writev() function returns the number of bytes written. On error, -1 is
returned, and
errno is set appropriately.
The errors are as given for
read(2) and
write(2). Additionally the
following error is defined.
- EINVAL
- The sum of the iov_len values overflows an
ssize_t value. Or, the vector count count is zero or greater
than MAX_IOVEC.
4.4BSD (the
readv and
writev functions first appeared in BSD 4.2),
Unix98, POSIX 1003.1-2001. Linux libc5 used
size_t as the type of the
count parameter, and
int as return type for these functions.
It is not advisable to mix calls to functions like
readv() or
writev(), which operate on file descriptors, with the functions from
the stdio library; the results will be undefined and probably not what you
want.
read(2),
write(2)
