home | help 
SENDFILE(2)		       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 argu-
     ment specifies how many bytes of the file should be sent, with 0 having 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 successfully writ-
     ten  is  returned	in  *sbytes  (if specified), and the error EAGAIN is re-
     turned.

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 4.7			November 5, 1998		     SENDFILE(2)
home | help