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TEE(1P)                    POSIX Programmer's Manual                   TEE(1P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       tee -- duplicate standard input
SYNOPSIS
       tee [-ai] [file...]
DESCRIPTION
       The tee utility shall copy standard input to standard output, making  a
       copy in zero or more files. The tee utility shall not buffer output.
       If  the  -a option is not specified, output files shall be written (see
       Section 1.1.1.4, File Read, Write, and Creation.
OPTIONS
       The tee utility  shall  conform  to  the  Base  Definitions  volume  of
       POSIX.1-2008, Section 12.2, Utility Syntax Guidelines.
       The following options shall be supported:
       -a        Append the output to the files.
       -i        Ignore the SIGINT signal.
OPERANDS
       The following operands shall be supported:
       file      A  pathname  of  an output file. If a file operand is '-', it
                 shall refer to a file  named  -;  implementations  shall  not
                 treat  it as meaning standard output.  Processing of at least
                 13 file operands shall be supported.
STDIN
       The standard input can be of any type.
INPUT FILES
       None.
ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of tee:
       LANG      Provide a default value for  the  internationalization  vari-
                 ables  that are unset or null. (See the Base Definitions vol-
                 ume of POSIX.1-2008, Section 8.2, Internationalization  Vari-
                 ables  for  the  precedence of internationalization variables
                 used to determine the values of locale categories.)
       LC_ALL    If set to a non-empty string value, override  the  values  of
                 all the other internationalization variables.
       LC_CTYPE  Determine  the  locale for the interpretation of sequences of
                 bytes of text data as characters (for example, single-byte as
                 opposed to multi-byte characters in arguments).
       LC_MESSAGES
                 Determine the locale that should be used to affect the format
                 and contents  of  diagnostic  messages  written  to  standard
                 error.
       NLSPATH   Determine the location of message catalogs for the processing
                 of LC_MESSAGES.
ASYNCHRONOUS EVENTS
       Default, except that if the -i option was specified,  SIGINT  shall  be
       ignored.
STDOUT
       The standard output shall be a copy of the standard input.
STDERR
       The standard error shall be used only for diagnostic messages.
OUTPUT FILES
       If  any file operands are specified, the standard input shall be copied
       to each named file.
EXTENDED DESCRIPTION
       None.
EXIT STATUS
       The following exit values shall be returned:
        0    The standard input was successfully copied to all output files.
       >0    An error occurred.
CONSEQUENCES OF ERRORS
       If a write to any successfully opened file  operand  fails,  writes  to
       other  successfully opened file operands and standard output shall con-
       tinue, but the exit status shall be non-zero.  Otherwise,  the  default
       actions specified in Section 1.4, Utility Description Defaults apply.
       The following sections are informative.
APPLICATION USAGE
       The  tee  utility  is usually used in a pipeline, to make a copy of the
       output of some utility.
       The file operand is technically optional, but tee  is  no  more  useful
       than cat when none is specified.
EXAMPLES
       Save an unsorted intermediate form of the data in a pipeline:
           ... | tee unsorted | sort > sorted
RATIONALE
       The  buffering  requirement  means that tee is not allowed to use ISO C
       standard fully buffered or line-buffered writes. It does not mean  that
       tee has to do 1-byte reads followed by 1-byte writes.
       It  should  be  noted  that  early  versions  of BSD ignore any invalid
       options and accept a single '-' as an alternative  to  -i.   They  also
       print a message if unable to open a file:
           "tee: cannot access %s\n", <pathname>
       Historical  implementations ignore write errors. This is explicitly not
       permitted by this volume of POSIX.1-2008.
       Some historical implementations  use  O_APPEND  when  providing  append
       mode;  others use the lseek() function to seek to the end-of-file after
       opening the file without O_APPEND. This volume of POSIX.1-2008 requires
       functionality  equivalent  to using O_APPEND; see Section 1.1.1.4, File
       Read, Write, and Creation.
FUTURE DIRECTIONS
       None.
SEE ALSO
       Chapter 1, Introduction, cat
       The Base Definitions volume of  POSIX.1-2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines
       The System Interfaces volume of POSIX.1-2008, lseek()
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                              TEE(1P)