Originální popis anglicky:
tee - duplicate standard input
Návod, kniha: POSIX Programmer's Manual
tee [-ai][file...]
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 .
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.
The following operands shall be supported:
- file
- A pathname of an output file. Processing of at least 13
file operands shall be supported.
The standard input can be of any type.
None.
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 .
Default, except that if the
-i option was specified, SIGINT shall be
ignored.
The standard output shall be a copy of the standard input.
The standard error shall be used only for diagnostic messages.
If any
file operands are specified, the standard input shall be copied to
each named file.
None.
The following exit values shall be returned:
- 0
- The standard input was successfully copied to all output
files.
- >0
- An error occurred.
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.
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.
Save an unsorted intermediate form of the data in a pipeline:
... | tee unsorted | sort > sorted
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 .
None.
Introduction ,
cat , the System Interfaces volume of
IEEE Std 1003.1-2001,
lseek()
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
.
