The <uio.h> header defines two functions useful for vector I/O operations, as well as the iovec structure they require.

Structures and Types ^TOP^

iovec Struct ^TOP^

Purpose

Defines an I/O vector; that is, a buffer address and size.

Declared In

posix/sys/uio.h

Prototype

struct iovec {

   void *iov_base;
   size_t iov_len;
}

Fields

iov_base

The base address of a memory region for input or output.

iov_len

The size of the memory pointed to by iov_base.

Functions and Macros ^TOP^

readv Function ^TOP^

Purpose

Performs the same action as read(), but scatters the input data into the iovcnt buffers specified by the members of the iov array: iov[0], iov[1], ..., iov[iovcnt-1].

Declared In

posix/sys/uio.h

Prototype

ssize_t readv (
   int d,
   const struct iovec *iov,
   size_t iovcnt
)

Parameters

→ d

The position to start reading from.

→ iov

The array.

→ iovcnt

The buffer.

Returns

Returns the number of bytes actually read and placed in the buffer. Zero (0) is returned if end-of-file is read. Otherwise, -1 is returned and the global variable errno is set to indicate the error.

See Also

read()

writev Function ^TOP^

Purpose

Performs the same action as write(), but gathers the output data from the iovcnt buffers specified by the members of the iov array: iov[0], iov[1], ..., iov[iovcnt-1].

Declared In

posix/sys/uio.h

Prototype

ssize_t writev (
   int d,
   const struct iovec *iov,
   size_t iovcnt
)

Parameters

→ d

The position to start gathering from.

→ iov

The array.

→ iovcnt

The buffer.

Returns

Returns the number of bytes actually written. Otherwise, -1 is returned and the global variable errno is set to indicate the error.

See Also

write()