1.\" Copyright (c) 1998, David Greenman 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice unmodified, this list of conditions, and the following 9.\" disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd November 5, 1998 29.Dt SENDFILE 2 30.Os 31.Sh NAME 32.Nm sendfile 33.Nd send a file to a socket 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.Fd #include <sys/types.h> 38.Fd #include <sys/socket.h> 39.Fd #include <sys/uio.h> 40.Ft int 41.Fn sendfile "int fd" "int s" "off_t offset" "size_t nbytes" "struct sf_hdtr *hdtr" "off_t *sbytes" "int flags" 42.Sh DESCRIPTION 43.Fn Sendfile 44sends a regular file specified by descriptor 45.Fa fd 46out a stream socket specified by descriptor 47.Fa s . 48.Pp 49The 50.Fa offset 51argument specifies where to begin in the file. 52The 53.Fa nbytes 54argument specifies how many bytes of the file should be sent, with 0 having the special 55meaning of send until the end of file has been reached. 56.Pp 57An optional header and/or trailer can be sent before and after the file data by specifying 58a pointer to a struct sf_hdtr, which has the following structure: 59.Pp 60.Bd -literal -offset indent -compact 61struct sf_hdtr { 62 struct iovec *headers; /* pointer to header iovecs */ 63 int hdr_cnt; /* number of header iovecs */ 64 struct iovec *trailers; /* pointer to trailer iovecs */ 65 int trl_cnt; /* number of trailer iovecs */ 66}; 67.Ed 68.Pp 69The 70.Fa headers 71and 72.Fa trailers 73pointers, if non-NULL, point to arrays of struct iovec structures. 74See the 75.Fn writev 76system call for information on the iovec structure. 77The number of iovecs in these 78arrays is specified by 79.Fa hdr_cnt 80and 81.Fa trl_cnt . 82.Pp 83If non-NULL, the system will write the total number of bytes sent on the socket to the 84variable pointed to by 85.Fa sbytes . 86.Pp 87The 88.Fa flags 89argument is currently undefined and should be specified as 0. 90.Pp 91When using a socket marked for non-blocking I/O, 92.Fn sendfile 93may send fewer bytes than requested. 94In this case, the number of bytes successfully 95written is returned in 96.Fa *sbytes 97(if specified), 98and the error 99.Er EAGAIN 100is returned. 101.Sh IMPLEMENTATION NOTES 102The 103.Fx 104implementation of 105.Fn sendfile 106is "zero-copy", meaning that it has been optimized so that copying of the file data is avoided. 107.Pp 108In the non-threaded library 109.Fn sendfile 110is implemented as the 111.Va sendfile 112syscall. 113.Pp 114In the threaded library, the 115.Va sendfile 116syscall is assembled to 117.Fn _thread_sys_sendfile 118and 119.Fn sendfile 120is implemented as a function which locks 121.Fa fd 122for reading and 123.Fa s 124for writing, then calls 125.Fn _thread_sys_sendfile . 126If the call to 127.Fn _thread_sys_sendfile 128would block, a context switch is performed. Before returning, 129.Fn sendfile 130unlocks 131.Fa fd 132and 133.Fa s . 134.Sh RETURN VALUES 135Upon successful completion, 136.Fn sendfile 137returns 0. Otherwise a -1 is returned and the global variable 138.Va errno 139is set to indicate the error. 140.Sh ERRORS 141.Bl -tag -width Er 142.It Bq Er EBADF 143.Fa fd 144is not a valid file descriptor. 145.It Bq Er EBADF 146.Fa s 147is not a valid socket descriptor. 148.It Bq Er ENOTSOCK 149.Fa s 150is not a socket. 151.It Bq Er EINVAL 152.Fa fd 153is not a regular file. 154.It Bq Er EINVAL 155.Fa s 156is not a SOCK_STREAM type socket. 157.It Bq Er EINVAL 158.Fa offset 159is negative or out of range. 160.It Bq Er ENOTCONN 161.Fa s 162points to an unconnected socket. 163.It Bq Er EPIPE 164The socket peer has closed the connection. 165.It Bq Er EIO 166An error occurred while reading from 167.Fa fd . 168.It Bq Er EFAULT 169An invalid address was specified for a parameter. 170.It Bq Er EAGAIN 171The socket is marked for non-blocking I/O and not all data was sent due to the socket buffer being filled. 172If specified, the number of bytes successfully sent will be returned in 173.Fa *sbytes . 174.El 175.Sh SEE ALSO 176.Xr open 2 , 177.Xr send 2 , 178.Xr socket 2 , 179.Xr writev 2 180.Sh HISTORY 181.Fn sendfile 182first appeared in 183.Fx 3.0 . 184This manual page first appeared in 185.Fx 3.1 . 186.Sh AUTHORS 187.Fn sendfile 188and this manual page were written by 189.An David Greenman Aq [email protected] . 190