writev()

Write bytes to a file

Synopsis:

#include <sys/uio.h>
#include <unistd.h>

ssize_t writev( int fildes,
                const iov_t* iov,
                int iovcnt );

Arguments:

fildes

The file descriptor for the file you want to write in.

iov

An array of iov_t objects that contain the data that you want to write.

iovcnt

The number of elements in the array.

Library:

libc

Description:

The writev() function 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].

For writev(), the iov_t structure contains the following members:

iov_base

Base address of a memory area from which data should be written.

iov_len

The length of the memory area.

The writev() function always writes a complete area before proceeding to the next.

The maximum number of entries in the iov array is UIO_MAXIOV.

Note that writev() ignores advisory locks that may have been set by the fcntl() function.

If writev() is interrupted by a signal before it has written any data, it returns a value of -1, and errno is set to EINTR. However, if writev() is interrupted by a signal after it has successfully written some data, it will return the number of bytes written.

For more details, see the write() function.

Returns:

The number of bytes written, or -1 if an error occurs (errno is set).

Errors:

EAGAIN

The O_NONBLOCK flag is set for the file descriptor, and the process would be delayed in the write operation.

EBADF

The file descriptor, fildes, isn't a valid file descriptor open for writing.

EFBIG

File is too big.

EINTR

The write operation was interrupted by a signal, and either no data was transferred, or the resource manager responsible for that file doesn't report partial transfers.

EINVAL

The iovcnt argument is less than or equal to 0, or greater than UIO_MAXIOV.

EIO

A physical I/O error occurred (for example, a bad block on a disk). The precise meaning is device-dependent.

ENOSPC

There is no free space remaining on the device containing the file.

ENOSYS

The write() function isn't implemented for the filesystem specified by filedes.

EPIPE

An attempt was made to write to a pipe (or FIFO) that isn't open for reading by any process. A SIGPIPE signal is also sent to the process.

Classification:

Standard Unix

See also:

close(), creat(), dup(), dup2(), errno, fcntl(), lseek(), open(), pipe(), read(), readv(), select(), write()