|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
|
ECHO(1P) POSIX Programmer's Manual ECHO(1P)
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.
echo — write arguments to standard output
echo [string...]
The echo utility writes its arguments to standard output, followed by
a <newline>. If there are no arguments, only the <newline> is
written.
The echo utility shall not recognize the "−−" argument in the manner
specified by Guideline 10 of the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines; "−−" shall be
recognized as a string operand.
Implementations shall not support any options.
The following operands shall be supported:
string A string to be written to standard output. If the first
operand is −n, or if any of the operands contain a
<backslash> character, the results are implementation-
defined.
On XSI-conformant systems, if the first operand is −n, it
shall be treated as a string, not an option. The following
character sequences shall be recognized on XSI-conformant
systems within any of the arguments:
\a Write an <alert>.
\b Write a <backspace>.
\c Suppress the <newline> that otherwise follows the
final argument in the output. All characters
following the '\c' in the arguments shall be
ignored.
\f Write a <form-feed>.
\n Write a <newline>.
\r Write a <carriage-return>.
\t Write a <tab>.
\v Write a <vertical-tab>.
\\ Write a <backslash> character.
\0num Write an 8-bit value that is the zero, one, two, or
three-digit octal number num.
Not used.
None.
The following environment variables shall affect the execution of
echo:
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.
Default.
The echo utility arguments shall be separated by single <space>
characters and a <newline> character shall follow the last argument.
Output transformations shall occur based on the escape sequences in
the input. See the OPERANDS section.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
It is not possible to use echo portably across all POSIX systems
unless both −n (as the first argument) and escape sequences are
omitted.
The printf utility can be used portably to emulate any of the
traditional behaviors of the echo utility as follows (assuming that
IFS has its standard value or is unset):
* The historic System V echo and the requirements on XSI
implementations in this volume of POSIX.1‐2008 are equivalent to:
printf "%b\n$*"
* The BSD echo is equivalent to:
if [ "X$1" = "X−n" ]
then
shift
printf "%s$*"
else
printf "%s\n$*"
fi
New applications are encouraged to use printf instead of echo.
None.
The echo utility has not been made obsolescent because of its
extremely widespread use in historical applications. Conforming
applications that wish to do prompting without <newline> characters
or that could possibly be expecting to echo a −n, should use the
printf utility derived from the Ninth Edition system.
As specified, echo writes its arguments in the simplest of ways. The
two different historical versions of echo vary in fatally
incompatible ways.
The BSD echo checks the first argument for the string −n which causes
it to suppress the <newline> that would otherwise follow the final
argument in the output.
The System V echo does not support any options, but allows escape
sequences within its operands, as described for XSI implementations
in the OPERANDS section.
The echo utility does not support Utility Syntax Guideline 10 because
historical applications depend on echo to echo all of its arguments,
except for the −n option in the BSD version.
None.
printf(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
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 .
IEEE/The Open Group 2013 ECHO(1P)
Pages that refer to this page: printf(1p), sh(1p), xargs(1p)
|
HTML rendering created 2018-02-02 by Michael Kerrisk, author of The Linux Programming Interface, maintainer of the Linux man-pages project. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.
|
|