READV (3)

SYNOPSIS

#include <sys/uio.h>
  int readv(int  filedes , const struct iovec * vector ,  
            size_t  count );  
  int writev(int  filedes , const struct iovec * vector ,  
            size_t  count );  

DESCRIPTION

The readv() function reads count blocks from the file associated with the file descriptor filedes 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 filedes .

The pointer vector points to a struct iovec defined in <sys/uio.h> as

10
struct iovect
{
14
void *iovbase;  /* Starting address  */
size_t iov_len;    /* Number of bytes */
10
} ;

Buffers are processed in the order vector[0] , vector[1] , ... vector[count] .

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.

RETURN VALUES

The readv() function returns the number of bytes or -1 on error; the writev() function returns the number of bytes written.

ERRORS

The readv() and writev() functions can fail and set errno to the following values:

EBADF

fd is not a valid file descriptor.

EINVAL

fd is unsuitable for reading (for readv() ) or writing (for writev() ).

EFAULT

buf is outside the processes' address space.

EAGAIN

Non-blocking I/O had been selected in the open() call, and reading or writing could not be done immediately.

EINTR

Reading or writing was interrupted before any data was transferred.

CONFORMING TO

unknown

BUGS

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.

SEE ALSO

- read (2) - - write (2) - man3/malloc 3