sendfile(3EXT)						    Extended Library Functions						    sendfile(3EXT)

NAME

       sendfile - send files over sockets or copy files to files

SYNOPSIS

       cc [ flag... ] file... -lsendfile [ library... ]
       #include <sys/sendfile.h>

       ssize_t sendfile(int out_fd, int in_fd, off_t *off, size_t len);

DESCRIPTION

       The  sendfile()	function  copies  data from in_fd to out_fd starting at offset off and of length len bytes. The in_fd argument should be a
       file descriptor to a regular file opened for reading. See open(2). The out_fd argument should be a file descriptor to a regular file opened
       for writing or to a connected AF_INET or AF_INET6 socket of SOCK_STREAM type. See socket(3SOCKET). The off argument is a pointer to a vari-
       able holding the input file pointer position from which the data will be read. After sendfile() has completed, the variable will be set	to
       the  offset  of	the byte following the last byte that was read. The sendfile() function does not modify the current file pointer of in_fd,
       but does modify the file pointer for out_fd if it is a regular file.

       The sendfile() function can also be used to send buffers by pointing in_fd to SFV_FD_SELF.

RETURN VALUES

       Upon successful completion, sendfile() returns the total number of bytes written to out_fd and also updates the offset to point to the byte
       that follows the last byte read. Otherwise, it returns -1, and errno is set to indicate the error.

ERRORS

       The sendfile() function will fail if:

       EAFNOSUPPORT    The implementation does not support the specified address family for socket.

       EAGAIN	       Mandatory  file	or  record  locking is set on either the file descriptor or output file descriptor if it points at regular
		       files. O_NDELAY or O_NONBLOCK is  set, and there is a blocking record lock. An attempt has been made to write to  a  stream
		       that cannot accept data with the O_NDELAY or the O_NONBLOCK flag set.

       EBADF	       The  out_fd  or	in_fd  argument  is  either not a valid file descriptor, out_fd is not opened for writing. or in_fd is not
		       opened for reading.

       EINVAL	       The offset cannot be represented by the off_t structure, or the length is negative when cast to ssize_t.

       EIO	       An I/O error occurred while accessing the file system.

       ENOTCONN        The socket is not connected.

       EOPNOTSUPP      The socket type is not supported.

       EPIPE	       The out_fd argument is no longer connected to the peer endpoint.

       EINTR	       A signal was caught during the write operation and no data was transferred.

USAGE

       The sendfile() function has a transitional interface for 64-bit file offsets. See lf64(5).

EXAMPLES

       Example 1 Sending a Buffer Over a Socket

       The following example demonstrates how to send the buffer buf over a socket. At the end, it prints the number of bytes transferred over the
       socket from the buffer. It assumes that addr will be filled up appropriately, depending upon where to send the buffer.

	 int tfd;
	 off_t baddr;
	 struct sockaddr_in sin;
	 char buf[64 * 1024];
	 in_addr_t addr;
	 size_t len;

	 tfd = socket(AF_INET, SOCK_STREAM, 0);
	 if (tfd == -1) {
	     perror("socket");
	     exit(1);
	 }

	 sin.sin_family = AF_INET;
	 sin.sin_addr.s_addr = addr;	/* Fill in the	appropriate address. */
	 sin.sin_port = htons(2345);
	 if (connect(tfd, (struct sockaddr *)&sin, sizeof(sin))<0) {
	     perror("connect");
	     exit(1);
	 }

	 baddr = (off_t)buf;
	 len = sizeof(buf);
	 while (len > 0) {
	     ssize_t res;
	     res = sendfile(tfd, SFV_FD_SELF, &baddr, len);
	     if (res == -1)
		     if (errno != EINTR) {
			     perror("sendfile");
			     exit(1);
		     } else continue;
	     len -= res;
	 }

       Example 2 Transferring Files to Sockets

       The following program demonstrates a transfer of files to sockets:

	 int ffd, tfd;
	 off_t off;
	 struct sockaddr_in sin;
	 in_addr_t  addr;
	 int len;
	 struct stat stat_buf;
	 ssize_t len;

	 ffd = open("file", O_RDONLY);
	 if (ffd == -1) {
	     perror("open");
	     exit(1);
	 }

	 tfd = socket(AF_INET, SOCK_STREAM, 0);
	 if (tfd == -1) {
	     perror("socket");
	     exit(1);
	 }

	 sin.sin_family = AF_INET;
	 sin.sin_addr = addr;	 /* Fill in the  appropriate address. */
	 sin.sin_port = htons(2345);
	 if (connect(tfd, (struct sockaddr *) &sin, sizeof(sin)) <0) {
	     perror("connect");
	     exit(1);
	 }

	 if (fstat(ffd, &stat_buf) == -1) {
	     perror("fstat");
	     exit(1);
	 }

	 len = stat_buf.st_size;
	 while (len > 0) {
	     ssize_t res;
	     res = sendfile(tfd, ffd, &off, len);
	     if (res == -1)
		     if (errno != EINTR) {
			     perror("sendfile");
			     exit(1);
		     } else continue;
	     len -= res;
	 }

ATTRIBUTES

       See attributes(5)  for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       open(2), libsendfile(3LIB), sendfilev(3EXT), socket(3SOCKET), attributes(5), lf64(5)

SunOS 5.11							    31 May 2006 						    sendfile(3EXT)