echo(P)                                                 echo(P)





NAME
       echo - write arguments to standard output

SYNOPSIS
       echo [string ...]

DESCRIPTION
       The  echo  utility writes its arguments to standard out-
       put, followed by a <newline>. If there are no arguments,
       only the <newline> is written.

OPTIONS
       The  echo  utility shall not recognize the "--" argument
       in the manner specified by Guideline 10 of the Base Def-
       initions  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  (  '\'  )  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 fol-
       lowing 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 fol-
              lowing   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.



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 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 mes-
              sages 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. <img
       src="../images/opt-end.gif"  alt="[Option   End]"   bor-
       der="0">

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 fol-
       lows (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\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.

EXAMPLES
       None.

RATIONALE
       The echo utility has not been made  obsolescent  because
       of  its  extremely widespread use in historical applica-
       tions.  Conforming applications that wish to do  prompt-
       ing without <newline>s or that could possibly be expect-
       ing 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 sec-
       tion.

       The echo utility does not support Utility Syntax  Guide-
       line  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 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                      echo(P)
