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tee(P) tee(P)
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 internationaliza-
tion 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 cate-
gories.)
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 spec-
ified 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 alterna-
tive 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 pro-
viding 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 Operat-
ing System Interface (POSIX), The Open Group Base Speci-
fications Issue 6, Copyright (C) 2001-2003 by the Insti-
tute 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.open-
group.org/unix/online.html .
POSIX 2003 tee(P)
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