@comment The start of a function description is indicated by the following
@comment comment. This syntax is used by the script functxh.sh:
@comment @comment function <name>

@comment function writev

@node writev, io
@findex writev

@subheading Syntax

@example
#include <sys/uio.h>

ssize_t writev (int fd, const struct iovec *iov, int iovcnt);
@end example

@subheading Description

@code{writev()} performs a scatter-gather write to the specified file
descriptor @var{fd}.  A group of buffers described by the array @var{iov},
with @var{iovcnt} entries, is written to @var{fd} in a similar
way to @code{write()} (@pxref{write, , write, libc}).

@code{struct iovec} is defined as follows:

@example
struct iovec @{
	void   *iov_base;	/* Base address of a memory region for I/O */
	size_t  iov_len;	/* Size of memory region                   */
@};
@end example

@subheading Return Value

On successful completion the function returns the number of bytes written.
Otherwise, a value of -1 is returned and @var{errno} is set appropriately.

@table @samp

@item EINVAL
One of the following conditions is true:

@itemize @bullet
@item
The total length to write would overflow a @samp{ssize_t}.
@item
@var{iovcnt} was negative, zero or larger than @code{IOV_MAX}.
@end itemize

@end table

@subheading Portability

@portability posix, unix98

@subheading Example

@example
@end example