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 File Read, Write, and Creation .

OPTIONS

       The tee utility shall conform to the Base  Definitions  volume  of  IEEE Std 1003.1-2001,  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. 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 variables that are unset or null. (See the
              Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization  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  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 continue, but the exit  status  shall  be  non-zero.   Otherwise,  the
       default actions specified in 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
       IEEE Std 1003.1-2001.

       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 IEEE Std 1003.1-2001
       requires functionality equivalent to using O_APPEND; see File Read, Write, and Creation .

FUTURE DIRECTIONS

       None.

SEE ALSO

       Introduction , cat , the System Interfaces volume of IEEE Std 1003.1-2001, lseek()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. 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.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                                TEE(P)