Section (1) tee


Linux manual pages Section 1  

Name

tee — read from standard input and write to standard output and files

Synopsis

tee [OPTION...] [FILE...]

DESCRIPTION

Copy standard input to each FILE, and also to standard output.

−a, −−append

append to the given FILEs, do not overwrite

−i, −−ignore−interrupts

ignore interrupt signals

−p

diagnose errors writing to non pipes

−−output−error[=MODE/]

set behavior on write error. See MODE below

−−help

display this help and exit

−−version

output version information and exit

MODE determines behavior with write errors on the outputs:

_zsingle_quotesz_warn_zsingle_quotesz_

diagnose errors writing to any output

_zsingle_quotesz_warn−nopipe_zsingle_quotesz_

diagnose errors writing to any output not a pipe

_zsingle_quotesz_exit_zsingle_quotesz_

exit on error writing to any output

_zsingle_quotesz_exit−nopipe_zsingle_quotesz_

exit on error writing to any output not a pipe

The default MODE for the −p option is _zsingle_quotesz_warn−nopipe_zsingle_quotesz_. The default operation when −−output−error is not specified, is to exit immediately on error writing to a pipe, and diagnose errors writing to non pipe outputs.

AUTHOR

Written by Mike Parker, Richard M. Stallman, and David MacKenzie.

REPORTING BUGS

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>

Report any translation bugs to <https://translationproject.org/team/>

SEE ALSO

Full documentation <https://www.gnu.org/software/coreutils/tee>

or available locally via: info _zsingle_quotesz_(coreutils) tee invocation_zsingle_quotesz_

COPYRIGHT

Copyright © 2019 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

Section (2) tee


Linux manual pages Section 2  

Name

tee — duplicating pipe content

Synopsis

#define _GNU_SOURCE          /* See feature_test_macros(7) */
#include <fcntl.h>
ssize_t tee( int fd_in,
  int fd_out,
  size_t len,
  unsigned int flags);
 

DESCRIPTION

tee() duplicates up to len bytes of data from the pipe referred to by the file descriptor fd_in to the pipe referred to by the file descriptor fd_out. It does not consume the data that is duplicated from fd_in; therefore, that data can be copied by a subsequent splice(2).

flags is a bit mask that is composed by ORing together zero or more of the following values:

SPLICE_F_MOVE

Currently has no effect for tee(); see splice(2).

SPLICE_F_NONBLOCK

Do not block on I/O; see splice(2) for further details.

SPLICE_F_MORE

Currently has no effect for tee(), but may be implemented in the future; see splice(2).

SPLICE_F_GIFT

Unused for tee(); see vmsplice(2).

RETURN VALUE

Upon successful completion, 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 fd_in.

On error, tee() returns −1 and errno is set to indicate the error.

ERRORS

EAGAIN

SPLICE_F_NONBLOCK was specified in flags or one of the file descriptors had been marked as nonblocking (O_NONBLOCK), and the operation would block.

EINVAL

fd_in or fd_out does not refer to a pipe; or fd_in and fd_out refer to the same pipe.

ENOMEM

Out of memory.

VERSIONS

The tee() system call first appeared in Linux 2.6.17; library support was added to glibc in version 2.5.

CONFORMING TO

This system call is Linux-specific.

NOTES

Conceptually, tee() copies the data between the two pipes. In reality no real data copying takes place though: under the covers, tee() assigns data to the output by merely grabbing a reference to the input.

EXAMPLE

The example below implements a basic tee(1) program using the tee() system call. Here is an example of its use:

$ date |./a.out out.log | cat
Tue Oct 28 10:06:00 CET 2014
$ cat out.log
Tue Oct 28 10:06:00 CET 2014

Program source

#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>
, 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);
}

SEE ALSO

splice(2), vmsplice(2), pipe(7)

COLOPHON

This page is part of release 5.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man−pages/.


  This manpage is Copyright (C) 2006 Jens Axboe
and Copyright (C) 2006 Michael Kerrisk <mtk.manpagesgmail.com>

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