In the BSD (Open, Net and Free) ``echo.c'' source, the following comment
appears:

/* This utility may NOT do getopt(3) option parsing. */

What prevents ``getopt'' from being used in the ``echo'' command?

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On Jul 22, 8:15 pm, Bob Nelson <bnel...@nelsonbe.com> wrote:
> In the BSD (Open, Net and Free) ``echo.c'' source, the following comment
> appears:
>
> /* This utility may NOT do getopt(3) option parsing. */
>
> What prevents ``getopt'' from being used in the ``echo'' command?

At a guess, maybe something to do with echo being an important tool
and it being available on a minimal install, perhaps where getopt
isn't available.

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Bob Nelson wrote:
> In the BSD (Open, Net and Free) ``echo.c'' source, the following comment
> appears:
>
> /* This utility may NOT do getopt(3) option parsing. */
>
> What prevents ``getopt'' from being used in the ``echo'' command?

I would expect that it's because getopt swallows certain standard
sequences such as "--". In other words according to POSIX "echo -- foo"
must print "-- foo" but if getopt() was called it would print "foo".
This is purely speculative; I have not written a test.

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Roger Leigh wrote:

> Bob Nelson <bnelson@nelsonbe.com> writes:
> 
>
> Nothing.  GNU echo (coreutils) as well as the bash echo builtin
> support options (-e, -n etc.).  There might be some ancient reason for
> the BSD behaviour, but it's certainly neither universal nor required.

It is required by POSIX:

"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.

[...]

If the first operand is -n, or if any of the operands contain a
backslash ('') character, the results are implementation-defined."

Note that it says "operand" when referring to -n, not "option".

POSIX requires "echo -e foo" to output "-e foo", and as far as I'm
aware GNU echo and the builtin echo in bash are the _only_ versions
of echo that do not conform to this POSIX requirement.

--
Geoff Clare <netnews@gclare.org.uk>

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In article <7pken4-208.ln1@leafnode-msgid.gclare.org.uk>,
Geoff Clare  <netnews@gclare.org.uk> wrote:
>
>POSIX requires "echo -e foo" to output "-e foo", and as far as I'm
>aware GNU echo and the builtin echo in bash are the _only_ versions
>of echo that do not conform to this POSIX requirement.

zsh builtin echo doesn't either, even in "emulate sh" mode with BSD_ECHO
turned on.

--
Alan Curry
pacman@world.std.com

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