ECHO(1P)						     POSIX Programmer's Manual							  ECHO(1P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       echo - write arguments to standard output

SYNOPSIS

       echo [string ...]

DESCRIPTION

       The echo utility writes its arguments to standard output, followed by a <newline>. If there are no arguments, only the <newline>  is  writ-
       ten.

OPTIONS

       The  echo  utility  shall  not  recognize  the  "--"  argument  in  the	manner specified by Guideline 10 of the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines; "--" shall be recognized as a string operand.

       Implementations shall not support any options.

OPERANDS

       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 ( '' ) charac-
	      ter, 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>.

       
	      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>.

       

	      Write a <newline>.

       
	      Write a <carriage-return>.

       	
	      Write a <tab>.

       v
	      Write a <vertical-tab>.

       \
	      Write a backslash character.

       num
	      Write an 8-bit value that is the zero, one, two, or three-digit octal number num.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       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
	      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.

STDOUT

       The echo utility arguments shall be separated by single <space>s and a <newline> shall follow the last  argument.   Output  transformations
       shall occur based on the escape sequences in the input. See the OPERANDS section.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

	0     Successful completion.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       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 IEEE Std 1003.1-2001 are equivalent to:

	  printf "%b
" "$*"

	* The BSD echo is equivalent to:

	  if [ "X$1" = "X-n" ]
	  then
	      shift
	      printf "%s" "$*"
	  else
	      printf "%s
" "$*"
	  fi

       New applications are encouraged to use printf instead of echo.

EXAMPLES

       None.

RATIONALE

       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>s 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	incompati-
       ble 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.

FUTURE DIRECTIONS

       None.

SEE ALSO

       printf

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								  ECHO(1P)