Subject: Re: discrepency beteen /bin/echo and builtin echo of /bin/sh
To: None <current-users@NetBSD.ORG>
From: Greg A. Woods <>
List: current-users
Date: 06/09/2002 10:52:38
[ On Sunday, June 9, 2002 at 12:43:04 (+0100), Ben Harris wrote: ]
> Subject: Re: discrepency beteen /bin/echo and builtin echo of /bin/sh
> No.  Any option aside from -n is specifically disallowed by both
> POSIX.2-1992 and the forthcoming corrigendum to POSIX-2001.  This means that
> "echo -e foo" MUST send "-e foo\n" to stdout.

Yeah, and POSIX is god.  I'd much rather stick to SuSv2 for anything
"real".  At least it's more practical and pragmatic.  POSIX is stuck in
the early 1980's and will undoutably stay there for decades to come,
esp. if ISO keeps oversight on it.  POSIX never was practical, not ever,

However, I will note the copy of the D11.2 draft I have didn't go so far
as you say the final 1992 edition did.  It only disallows '--'.  It
allows any options, specifically un-defines the behaviour of '-n' as the
first option (and un-defines the behaviour of backslashes in any
strings), but doesn't require any options (nor does it require support
for backslashes).

Are you sure you're not mis-reading the 1992 edition?

[[ starting page 475, P1003.2/D11.2 1991 ]]

 4.19  echo - Write arguments to standard output

 4.19.1  Synopsis

 echo  [string ...]

 4.19.2  Description

 The echo utility shall write its arguments to standard output, followed
 by a <newline> character.  If there are no arguments, only the <newline>
 character shall be written.

 4.19.3  Options

 The echo utility shall not recognize the -- argument in the manner
 specified by utility syntax guideline 10 in 2.10.2; -- shall be
 recognized as a string operand.

 Implementations need not support any options.

 4.19.4  Operands

 The following operands shall be supported by the implementation:

    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

 4.19.5  External Influences  Standard Input

 None.  Input Files

 None.  Environment Variables

 The following environment variables shall affect the execution of echo:

    LANG               This variable shall determine the locale to use for
                       the locale categories when both LC_ALL and the
                       corresponding environment variable (beginning with
                       LC_) do not specify a locale.  See 2.6.

    LC_ALL             This variable shall determine the locale to be used
                       to override any values for locale categories
                       specified by the settings of LANG or any
                       environment variables beginning with LC_.

    LC_MESSAGES        This variable shall determine the language in which
                       diagnostic messages should be written.  Asynchronous Events


 4.19.6  External Effects  Standard Output

 The echo utility arguments shall be separated by single <space>s and a
 <newline> character shall follow the last argument.  Standard Error

 Used only for diagnostic messages.  Output Files


 4.19.7  Extended Description


 4.19.8  Exit Status

 The echo utility shall exit with one of the following values:

     0    Successful completion.

    >0    An error occurred.

 4.19.9  Consequences of Errors



 4.19.10  Rationale. (This subclause is not a part of P1003.2)


 As specified by this standard, echo writes its arguments in the simplest
 of ways.  The two different historical versions of echo vary in fatal
 incompatible ways.

 The BSD echo checks the first argument for the string "-n", which causes
 it to suppress the <newline> character 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:

    \a    Write an <alert> character.

    \b    Write a <backspace> character.

    \c    Suppress the <newline> character that otherwise follows the
          final argument in the output.  All characters following the \c
          in the arguments are ignored.

    \f    Write a <form-feed> character.

    \n    Write a <newline> character.

    \r    Write a <carriage-return> character.

    \t    Write a <tab> character.

    \v    Write a <vertical-tab> character.

    \\    Write a backslash character.

          Write an 8-bit value that is the 1-, 2-, or 3-digit octal number

 It is not possible to use echo portably across these two implementations
 unless both -n (as the first argument) and escape sequences are omitted.

 The printf utility (see 4.50) can be used to portably emulate any of the
 traditional behaviors of the echo utility as follows:

     - The System V echo is equivalent to:

             printf "%b\n" "$*"

     - The BSD echo is equivalent to:

             if [ "X$1" = "X-n" ]
                     printf "%s" "$*"
                     printf "%s\n" "$*"

 The echo utility does not support utility syntax guideline 10 because
 existing applications depend on echo to echo all of its arguments, except
 for the -n option in the BSD version.

 New applications are encouraged to use printf instead of echo.  The echo
 utility has not been made obsolescent because of its extremely widespread
 use in existing applications.

               Copyright c 1991 IEEE.  All rights reserved.
      This is an unapproved IEEE Standards Draft, subject to change.

 478                                     4 Execution Environment Utilities

								Greg A. Woods

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