xenial (1) tee.1posix.gz

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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 variables that are unset or null. (See the
                 Base  Definitions  volume  of POSIX.1‐2008, 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 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()


       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 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.kernel.org/doc/man-pages/reporting_bugs.html .