readv

readv

Reads Data from a Socket Descriptor into an Array of Buffers

Portability: UNIX compatible

SYNOPSIS
DESCRIPTION
RETURN VALUE
CAUTION
PORTABILITY
RELATED FUNCTIONS

SYNOPSIS

#include <sys/types.h>
#include <sys/uio.h>
#include <fcntl.h>

int readv(int s, struct iovec *iov, int iovcnt);

DESCRIPTION

readv reads data from socket or file descriptor s into the iovcnt buffers specified by the iov array. As with the read call, the socket must have been previously associated with a remote address via the connect system call. If there are no data, readv blocks the caller unless the socket is in non-blocking mode. The iovec structure is defined in <sys/uio.h> . Each iovec entry specifies the base address and length of an area in memory in which the data should be placed. readv completely fills one area before proceeding to the next area.

Note: Although readv is primarily used with sockets, it can also be used to read any file that can be accessed by the read function. [cautionend]

RETURN VALUE

If readv succeeds, it returns the number of bytes read into the buffer. If readv returns a 0 , the end-of-file has been reached. If readv fails, it returns a -1 . It is common for readv to return a value less than the total number of bytes in the buffers. This is not an error.

CAUTION

readv is an atomic operation. With UDP, no more than one datagram can be read per call. If you are using datagram sockets, make sure that there is enough buffer space in the I/O vector to contain an incoming datagram.

PORTABILITY

readv is portable to other environments, including most UNIX systems, that implement BSD sockets.

RELATED FUNCTIONS

connect , recv , recvfrom , recvmsg , write , writev

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