188 lines
5.0 KiB
Groff
188 lines
5.0 KiB
Groff
.\" Copyright (c) 1998, David Greenman
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice unmodified, this list of conditions, and the following
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.\" disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 5, 1998
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.Dt SENDFILE 2
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.Os
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.Sh NAME
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.Nm sendfile
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.Nd send a file to a socket
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/socket.h>
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.Fd #include <sys/uio.h>
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.Ft int
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.Fn sendfile "int fd" "int s" "off_t offset" "size_t nbytes" "struct sf_hdtr *hdtr" "off_t *sbytes" "int flags"
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.Sh DESCRIPTION
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.Fn Sendfile
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sends a regular file specified by descriptor
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.Fa fd
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out a stream socket specified by descriptor
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.Fa s .
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.Pp
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The
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.Fa offset
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argument specifies where to begin in the file.
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The
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.Fa nbytes
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argument specifies how many bytes of the file should be sent, with 0 having the special
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meaning of send until the end of file has been reached.
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.Pp
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An optional header and/or trailer can be sent before and after the file data by specifying
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a pointer to a struct sf_hdtr, which has the following structure:
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.Pp
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.Bd -literal -offset indent -compact
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struct sf_hdtr {
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struct iovec *headers; /* pointer to header iovecs */
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int hdr_cnt; /* number of header iovecs */
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struct iovec *trailers; /* pointer to trailer iovecs */
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int trl_cnt; /* number of trailer iovecs */
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};
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.Ed
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.Pp
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The
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.Fa headers
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and
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.Fa tailers
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pointers, if non-NULL, point to arrays of struct iovec structures.
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See the
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.Fn writev
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system call for information on the iovec structure.
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The number of iovecs in these
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arrays is specified by
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.Fa hdr_cnt
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and
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.Fa trl_cnt .
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.Pp
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If non-NULL, the system will write the total number of bytes sent on the socket to the
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variable pointed to by
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.Fa sbytes .
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.Pp
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The
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.Fa flags
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argument is currently undefined and should be specified as 0.
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.Pp
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When using a socket marked for non-blocking I/O,
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.Fn sendfile
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may send fewer bytes than requested.
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In this case, the number of bytes successfully
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written is returned in
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.Fa *sbytes
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(if specified),
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and the error
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.Er EAGAIN
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is returned.
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.Sh IMPLEMENTATION NOTES
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The FreeBSD implementation of
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.Fn sendfile
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is "zero-copy", meaning that it has been optimized so that copying of the file data is avoided.
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.Pp
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In the non-threaded library
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.Fn sendfile
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is implemented as the
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.Va sendfile
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syscall.
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.Pp
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In the threaded library, the
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.Va sendfile
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syscall is assembled to
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.Fn _thread_sys_sendfile
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and
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.Fn sendfile
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is implemented as a function which locks
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.Fa fd
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for reading and
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.Fa s
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for writing, then calls
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.Fn _thread_sys_sendfile .
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If the call to
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.Fn _thread_sys_sendfile
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would block, a context switch is performed. Before returning,
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.Fn sendfile
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unlocks
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.Fa fd
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and
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.Fa s .
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.Sh RETURN VALUES
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Upon successful completion,
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.Fn sendfile
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returns 0. Otherwise a -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa fd
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is not a valid file descriptor.
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.It Bq Er EBADF
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.Fa s
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is not a valid socket descriptor.
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.It Bq Er ENOTSOCK
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.Fa s
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is not a socket.
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.It Bq Er EINVAL
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.Fa fd
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is not a regular file.
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.It Bq Er EINVAL
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.Fa s
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is not a SOCK_STREAM type socket.
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.It Bq Er EINVAL
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.Fa offset
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is negative or out of range.
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.It Bq Er ENOTCONN
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.Fa s
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points to an unconnected socket.
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.It Bq Er EPIPE
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The socket peer has closed the connection.
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.It Bq Er EIO
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An error occurred while reading from
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.Fa fd .
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.It Bq Er EFAULT
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An invalid address was specified for a parameter.
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.It Bq Er EAGAIN
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The socket is marked for non-blocking I/O and not all data was sent due to the socket buffer being filled.
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If specified, the number of bytes successfully sent will be returned in
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.Fa *sbytes .
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.El
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.Sh SEE ALSO
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.Xr open 2 ,
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.Xr send 2 ,
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.Xr socket 2 ,
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.Xr writev 2
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.Sh HISTORY
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.Fn sendfile
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first appeared in
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.Fx 3.0 .
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This manual page first appeared in
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.Fx 3.1 .
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.Sh AUTHORS
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.Fn sendfile
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and this manual page were written by
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.An David Greenman Aq dg@root.com .
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