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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.  Pro-
		 cessing 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 variables that are unset or
		 null.	(See  the  Base Definitions volume of POSIX.1-2008, Section 8.2, Interna-
		 tionalization Variables 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 inter-
		 nationalization 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 continue, 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  util-
       ity.

       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 fol-
       lowed by 1-byte writes.

       It should be noted that early versions of BSD ignore any invalid options and accept a sin-
       gle '-' 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  Electrical  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  discrep-
       ancy  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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group			       2013					  TEE(1P)
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