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SENDFILE(2)		  FreeBSD System Calls Manual		   SENDFILE(2)

NAME
     sendfile -- send a	file to	a socket

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>
     #include <sys/uio.h>

     int
     sendfile(int fd, int s, off_t offset, size_t nbytes,
	 struct	sf_hdtr	*hdtr, off_t *sbytes, int flags);

DESCRIPTION
     Sendfile()	sends a	regular	file specified by descriptor fd	out a stream
     socket specified by descriptor s.

     The offset	argument specifies where to begin in the file.	The nbytes
     argument specifies	how many bytes of the file should be sent, with	0 hav-
     ing the special meaning of	send until the end of file has been reached.

     An	optional header	and/or trailer can be sent before and after the	file
     data by specifying	a pointer to a struct sf_hdtr, which has the following
     structure:

	   struct sf_hdtr {
		   struct iovec	*headers;  /* pointer to header	iovecs */
		   int hdr_cnt;		   /* number of	header iovecs */
		   struct iovec	*trailers; /* pointer to trailer iovecs	*/
		   int trl_cnt;		   /* number of	trailer	iovecs */
	   };

     The headers and trailers pointers,	if non-NULL, point to arrays of	struct
     iovec structures.	See the	writev() system	call for information on	the
     iovec structure.  The number of iovecs in these arrays is specified by
     hdr_cnt and trl_cnt.

     If	non-NULL, the system will write	the total number of bytes sent on the
     socket to the variable pointed to by sbytes.

     The flags argument	is currently undefined and should be specified as 0.

     When using	a socket marked	for non-blocking I/O, sendfile() may send
     fewer bytes than requested.  In this case,	the number of bytes success-
     fully written is returned in *sbytes (if specified), and the error	EAGAIN
     is	returned.

IMPLEMENTATION NOTES
     The FreeBSD implementation	of sendfile() is "zero-copy", meaning that it
     has been optimized	so that	copying	of the file data is avoided.

RETURN VALUES
     The sendfile() function returns the value 0 if successful;	otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     [EBADF]		fd is not a valid file descriptor.

     [EBADF]		s is not a valid socket	descriptor.

     [ENOTSOCK]		s is not a socket.

     [EINVAL]		fd is not a regular file.

     [EINVAL]		s is not a SOCK_STREAM type socket.

     [EINVAL]		offset is negative or out of range.

     [ENOTCONN]		s points to an unconnected socket.

     [EPIPE]		The socket peer	has closed the connection.

     [EIO]		An error occurred while	reading	from fd.

     [EFAULT]		An invalid address was specified for a parameter.

     [EAGAIN]		The socket is marked for non-blocking I/O and not all
			data was sent due to the socket	buffer being filled.
			If specified, the number of bytes successfully sent
			will be	returned in *sbytes.

SEE ALSO
     open(2), send(2), socket(2), writev(2)

HISTORY
     sendfile()	first appeared in FreeBSD 3.0.	This manual page first
     appeared in FreeBSD 3.1.

AUTHORS
     sendfile()	and this manual	page were written by David Greenman
     <dg@root.com>.

FreeBSD	9.2		       November	5, 1998			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | AUTHORS

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