+++ /dev/null
-.\" This manpage is Copyright (C) 2006 Jens Axboe
-.\" and Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.TH TEE 2 2014-12-31 "Linux" "Linux Programmer's Manual"
-.SH NAME
-tee \- duplicating pipe content
-.SH SYNOPSIS
-.nf
-.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
-.B #include <fcntl.h>
-
-.BI "ssize_t tee(int " fd_in ", int " fd_out ", size_t " len \
-", unsigned int " flags );
-.fi
-.\" Return type was long before glibc 2.7
-.SH DESCRIPTION
-.\" Example programs http://brick.kernel.dk/snaps
-.\"
-.\"
-.\" add a "tee(in, out1, out2)" system call that duplicates the pages
-.\" (again, incrementing their reference count, not copying the data) from
-.\" one pipe to two other pipes.
-.BR tee ()
-duplicates up to
-.I len
-bytes of data from the pipe referred to by the file descriptor
-.I fd_in
-to the pipe referred to by the file descriptor
-.IR fd_out .
-It does not consume the data that is duplicated from
-.IR fd_in ;
-therefore, that data can be copied by a subsequent
-.BR splice (2).
-
-.I flags
-is a series of modifier flags, which share the name space with
-.BR splice (2)
-and
-.BR vmsplice (2):
-.TP 1.9i
-.B SPLICE_F_MOVE
-Currently has no effect for
-.BR tee ();
-see
-.BR splice (2).
-.TP
-.B SPLICE_F_NONBLOCK
-Do not block on I/O; see
-.BR splice (2)
-for further details.
-.TP
-.B SPLICE_F_MORE
-Currently has no effect for
-.BR tee (),
-but may be implemented in the future; see
-.BR splice (2).
-.TP
-.B SPLICE_F_GIFT
-Unused for
-.BR tee ();
-see
-.BR vmsplice (2).
-.SH RETURN VALUE
-Upon successful completion,
-.BR tee ()
-returns the number of bytes that were duplicated between the input
-and output.
-A return value of 0 means that there was no data to transfer,
-and it would not make sense to block, because there are no
-writers connected to the write end of the pipe referred to by
-.IR fd_in .
-
-On error,
-.BR tee ()
-returns \-1 and
-.I errno
-is set to indicate the error.
-.SH ERRORS
-.TP
-.B EAGAIN
-.B SPLICE_F_NONBLOCK
-was specified in
-.IR flags ,
-and the operation would block.
-.TP
-.B EINVAL
-.I fd_in
-or
-.I fd_out
-does not refer to a pipe; or
-.I fd_in
-and
-.I fd_out
-refer to the same pipe.
-.TP
-.B ENOMEM
-Out of memory.
-.SH VERSIONS
-The
-.BR tee ()
-system call first appeared in Linux 2.6.17;
-library support was added to glibc in version 2.5.
-.SH CONFORMING TO
-This system call is Linux-specific.
-.SH NOTES
-Conceptually,
-.BR tee ()
-copies the data between the two pipes.
-In reality no real data copying takes place though:
-under the covers,
-.BR tee ()
-assigns data in the output by merely grabbing
-a reference to the input.
-.SH EXAMPLE
-The example below implements a basic
-.BR tee (1)
-program using the
-.BR tee ()
-system call.
-Here is an example of its use:
-
-.in +4n
-.nf
-$ \fBdate |./a.out out.log | cat\fP
-Tue Oct 28 10:06:00 CET 2014
-$ \fBcat out.log\fP
-Tue Oct 28 10:06:00 CET 2014
-.fi
-.in
-.SS Program source
-.nf
-
-#define _GNU_SOURCE
-#include <fcntl.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <errno.h>
-#include <limits.h>
-
-int
-main(int argc, char *argv[])
-{
- int fd;
- int len, slen;
-
- if (argc != 2) {
- fprintf(stderr, "Usage: %s <file>\\n", argv[0]);
- exit(EXIT_FAILURE);
- }
-
- fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
- if (fd == \-1) {
- perror("open");
- exit(EXIT_FAILURE);
- }
-
- do {
- /*
- * tee stdin to stdout.
- */
- len = tee(STDIN_FILENO, STDOUT_FILENO,
- INT_MAX, SPLICE_F_NONBLOCK);
-
- if (len < 0) {
- if (errno == EAGAIN)
- continue;
- perror("tee");
- exit(EXIT_FAILURE);
- } else
- if (len == 0)
- break;
-
- /*
- * Consume stdin by splicing it to a file.
- */
- while (len > 0) {
- slen = splice(STDIN_FILENO, NULL, fd, NULL,
- len, SPLICE_F_MOVE);
- if (slen < 0) {
- perror("splice");
- break;
- }
- len \-= slen;
- }
- } while (1);
-
- close(fd);
- exit(EXIT_SUCCESS);
-}
-.fi
-.SH SEE ALSO
-.BR splice (2),
-.BR vmsplice (2)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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