Re: [bug?] echo -n does not work as described

[Kevin Korb <kmk@sanitarium.net>]

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On 11/11/2015 10:14 PM, Eric Blake wrote:
> On 11/11/2015 06:56 PM, Kevin Korb wrote:
>> I am on dash version 0.5.8.2 on Gentoo Linux (USE=libedit
>> -static).
>> 
>> The echo builtin does not work as described.  In the man page:
> 
> Which man page? Coreutils'?

I was quoting the dash man page.  I did quote the result of the
coreutils version of echo (/bin/echo) which worked correctly.

> Read it further:
> 
>> NOTE: your shell may have its own version of echo, which usually
>> super‐ sedes the version described here. Please refer to your
>> shell's docu‐ mentation for details about the options it
>> supports.
> 
> By the way, 'echo -n' is non-portable, and POSIX says you should
> use 'printf' instead.

This isn't my problem.  I am trying to use dash as a replacement for
/bin/sh and it is failing horribly.  I am not the authors of the
problem scripts.  Plus, frankly, it is absurd to require printf where
echo [-n] should work correctly according to the dash documentation.

> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
>
>  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.
> 
>> $ echo -n testing -n testing
> 
> Dash's implementation-defined behavior for -n is to treat it the
> same as every other string.  Thus, this is not a bug in dash, at
> least according to POSIX.

Either this is a bug in dash or in dash's man page.  The man page is
clear about how echo and echo -n should work.  But the reality is very
different.

>> This is causing me problems when I attempt to switch /bin/sh from
>> bash to dash.

This isn't stuff I have written.  This is stuff that I am tired of
modifying to be dash compatible.

Either dash's echo command should operate as documented or the
documentation should be corrected.

> It's probably not the only bashism you've been relying on.  You may
> want to try using checkbashisms 
> (http://sourceforge.net/projects/checkbaskisms/) to help you find
> other portability pitfalls.
> 

- -- 
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	Kevin Korb			Phone:    (407) 252-6853
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	FutureQuest, Inc.		Kevin@FutureQuest.net  (work)
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