.\" @(#)write.2 8.5 (Berkeley) 4/2/94
.\" $FreeBSD: src/lib/libc/sys/write.2,v 1.12.2.7 2001/12/14 18:34:02 ru Exp $
.\"
-.Dd April 2, 1994
+.Dd March 18, 2015
.Dt WRITE 2
.Os
.Sh NAME
+.Nm pwrite ,
.Nm write ,
-.Nm writev ,
-.Nm pwrite
+.Nm pwritev ,
+.Nm writev
.Nd write output
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
-.In sys/types.h
-.In sys/uio.h
.In unistd.h
.Ft ssize_t
-.Fn write "int d" "const void *buf" "size_t nbytes"
+.Fo pwrite
+.Fa "int fildes"
+.Fa "const void *buf"
+.Fa "size_t nbyte"
+.Fa "off_t offset"
+.Fc
+.Ft ssize_t
+.Fo write
+.Fa "int fildes"
+.Fa "const void *buf"
+.Fa "size_t nbyte"
+.Fc
+.In sys/uio.h
.Ft ssize_t
-.Fn writev "int d" "const struct iovec *iov" "int iovcnt"
+.Fo writev
+.Fa "int fildes"
+.Fa "const struct iovec *iov"
+.Fa "int iovcnt"
+.Fc
.Ft ssize_t
-.Fn pwrite "int d" "const void *buf" "size_t nbytes" "off_t offset"
+.Fo pwritev
+.Fa "int fildes"
+.Fa "const struct iovec *iov"
+.Fa "int iovcnt"
+.Fa "off_t offset"
+.Fc
.Sh DESCRIPTION
-.Fn Write
+.Fn write
attempts to write
-.Fa nbytes
+.Fa nbyte
of data to the object referenced by the descriptor
-.Fa d
+.Fa fildes
from the buffer pointed to by
.Fa buf .
-.Fn Writev
+.Fn writev
performs the same action, but gathers the output data
from the
.Fa iovcnt
buffers specified by the members of the
.Fa iov
array: iov[0], iov[1], ..., iov[iovcnt\|-\|1].
-.Fn Pwrite
-performs the same function, but writes to the specified position in
+.Fn pwrite
+and
+.Fn pwritev
+perform the same functions, but write to the specified position in
the file without modifying the file pointer.
.Pp
For
-.Fn writev ,
+.Fn writev
+and
+.Fn pwritev ,
the
.Fa iovec
structure is defined as:
.Fa iovec
entry specifies the base address and length of an area
in memory from which data should be written.
-.Fn Writev
+.Fn writev
+and
+.Fn pwritev
will always write a complete area before proceeding
to the next.
.Pp
.Fn write
starts at a position
given by the pointer associated with
-.Fa d ,
+.Fa fildes ,
see
.Xr lseek 2 .
Upon return from
a writable set-user-id file
owned by the super-user.
.Pp
-When using non-blocking I/O on objects such as sockets that are subject
-to flow control,
+When using non-blocking I/O on objects, such as sockets,
+that are subject to flow control,
.Fn write
and
.Fn writev
the return value must be noted,
and the remainder of the operation should be retried when possible.
.Sh RETURN VALUES
-Upon successful completion the number of bytes which were written
-is returned. Otherwise a -1 is returned and the global variable
+Upon successful completion the number of bytes
+which were written is returned.
+Otherwise, a -1 is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
-.Fn Write ,
+The
+.Fn write ,
.Fn writev ,
+.Fn pwrite ,
+and
+.Fn pwritev
+system calls will fail and the file pointer will remain unchanged if:
+.Bl -tag -width Er
+.\" ===========
+.It Bq Er EDQUOT
+The user's quota of disk blocks on the file system
+containing the file is exhausted.
+.\" ===========
+.It Bq Er EFAULT
+Part of
+.Fa iov
+or data to be written to the file
+points outside the process's allocated address space.
+.\" ===========
+.It Bq Er EINVAL
+The pointer associated with
+.Fa fildes
+is negative.
+.El
+.Pp
+The
+.Fn write
and
.Fn pwrite
-will fail and the file pointer will remain unchanged if:
+system calls will fail and the file pointer will remain unchanged if:
.Bl -tag -width Er
+.\" ===========
+.It Bq Er EAGAIN
+The file is marked for non-blocking I/O,
+and no data could be written immediately.
+.\" ===========
.It Bq Er EBADF
-.Fa D
-is not a valid descriptor open for writing.
+.Fa fildes
+is not a valid file descriptor open for writing.
+.\" ===========
+.It Bq Er ECONNRESET
+A write is attempted on a socket that is not connected.
+.\" ===========
+.It Bq Er EFBIG
+An attempt is made to write a file that exceeds the process's
+file size limit or the maximum file size.
+.\" ===========
+.It Bq Er EFBIG
+The file is a regular file,
+.Fa nbyte
+is greater than 0,
+and the starting position is greater than or equal
+to the offset maximum established in the open file description
+associated with
+.Fa fildes .
+.\" ===========
+.It Bq Er EINTR
+A signal interrupts the write before it could be completed.
+.\" ===========
+.It Bq Er EIO
+An I/O error occurs while reading from or writing to the file system.
+.\" ===========
+.It Bq Er ENETDOWN
+A write is attempted on a socket
+and the local network interface used to reach the destination is down.
+.\" ===========
+.It Bq Er ENETUNREACH
+A write is attempted on a socket and no route to the network is present.
+.\" ===========
+.It Bq Er ENOSPC
+There is no free space remaining on the file system containing the file.
+.\" ===========
+.It Bq Er ENXIO
+A request is made of a nonexistent device,
+or the request is outside the capabilities of the device.
+.\" ===========
.It Bq Er EPIPE
An attempt is made to write to a pipe that is not open
for reading by any process.
+.\" ===========
.It Bq Er EPIPE
An attempt is made to write to a socket of type
.Dv SOCK_STREAM
that is not connected to a peer socket.
-.It Bq Er EFBIG
-An attempt was made to write a file that exceeds the process's
-file size limit or the maximum file size.
-.It Bq Er EFAULT
-Part of
-.Fa iov
-or data to be written to the file
-points outside the process's allocated address space.
-.It Bq Er EINVAL
-The pointer associated with
-.Fa d
-was negative.
-.It Bq Er ENOSPC
-There is no free space remaining on the file system
-containing the file.
-.It Bq Er EDQUOT
-The user's quota of disk blocks on the file system
-containing the file has been exhausted.
-.It Bq Er EIO
-An I/O error occurred while reading from or writing to the file system.
-.It Bq Er EINTR
-A signal interrupted the write before it could be completed.
+.El
+.Pp
+The
+.Fn write
+and
+.Fn writev
+calls may also return the following errors:
+.Bl -tag -width Er
+.\" ===========
.It Bq Er EAGAIN
-The file was marked for non-blocking I/O,
-and no data could be written immediately.
+See EWOULDBLOCK, below.
+.\" ===========
+.It Bq Er EWOULDBLOCK
+The file descriptor is for a socket, is marked O_NONBLOCK,
+and write would block.
+The exact error code depends on the protocol,
+but EWOULDBLOCK is more common.
.El
.Pp
In addition,
.Fn writev
may return one of the following errors:
.Bl -tag -width Er
+.\" ===========
.It Bq Er EDESTADDRREQ
The destination is no longer available when writing to a
.Ux
domain datagram socket on which
.Xr connect 2
+or
+.Xr connectx 2
had been used to set a destination address.
+.\" ===========
+.It Bq Er ENOBUFS
+The mbuf pool has been completely exhausted when writing to a socket.
+.El
+.Pp
+The
+.Fn writev
+and
+.Fn pwritev
+calls may also return the following errors:
+.Bl -tag -width Er
+.\" ===========
.It Bq Er EINVAL
.Fa Iovcnt
-was less than or equal to 0, or greater than
+is less than or equal to 0, or greater than
.Dv UIO_MAXIOV .
+.\" ===========
.It Bq Er EINVAL
One of the
.Fa iov_len
values in the
.Fa iov
-array was negative.
+array is negative.
+.\" ===========
.It Bq Er EINVAL
The sum of the
.Fa iov_len
values in the
.Fa iov
-array overflowed a 32-bit integer.
-.It Bq Er ENOBUFS
-The mbuf pool has been completely exhausted when writing to a socket.
+array overflows a 32-bit integer.
.El
.Pp
The
.Fn pwrite
-call may also return the following errors:
+and
+.Fn pwritev
+calls may also return the following errors:
.Bl -tag -width Er
+.\" ===========
.It Bq Er EINVAL
The specified file offset is invalid.
+.\" ===========
.It Bq Er ESPIPE
The file descriptor is associated with a pipe, socket, or FIFO.
.El
+.Sh LEGACY SYNOPSIS
+.Fd #include <sys/types.h>
+.Fd #include <sys/uio.h>
+.Fd #include <unistd.h>
+.Pp
+These include files are needed for all three functions.
.Sh SEE ALSO
.Xr fcntl 2 ,
.Xr lseek 2 ,
.Xr open 2 ,
.Xr pipe 2 ,
-.Xr select 2
+.Xr select 2 ,
+.Xr compat 5
.Sh STANDARDS
The
.Fn write
.Fn pwrite
functions are expected to conform to
.St -xpg4.2 .
+.Fn pwritev
+is nonstandard.
.Sh HISTORY
The
.Fn pwrite
projects / apple / xnu.git / blobdiff