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 .