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bug#23090: true and false not POSIX

From: Eric Blake
Subject: bug#23090: true and false not POSIX
Date: Tue, 22 Mar 2016 09:13:40 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 03/22/2016 06:43 AM, Ruediger Meier wrote:
> Hi,
> Is there any good reason why coreutils true and false are not POSIX?

No, because coreutils' true and false ARE compliant with POSIX.

> But coreutils true has --version and --help implemented. It needs 
>> /dev/null redirection to work as expected.

Not true.  POSIX says that behavior is unspecified for 'true --help'.
Therefore, whatever coreutils does in that case does not violate POSIX.

'true -- --help', on the other hand, must be silent - but coreutils
obeys that rule.

> Also these options are the reason why true.c is using many library 
> functions like setlocale, etc. The binary is bloated and the risk that 
> something goes wrong/crashs is much higher. I was looking for a minimal 
> and rock-solid true command to be used in scripts.

If coreutils' true crashes due to wrong file permissions causing
setlocale() to fail, your system is already going to have severe
problems with other utilities.  Coreutils is complying with GNU Coding
Standards at the same time as POSIX, and we do not feel that it is
bloated for doing so.

> IMO it is not worth to violate POSIX just because of cosmetical reasons 
> (--help/--version). Moreover since the true command usually comes from 
> the shell I guess that almost no person on earth ever had seen your 
> nice --help output anyways.

On many GNU/Linux systems, 'man true' displays the coreutils' man page
for true, which in turn was generated from 'true --help' output.  So a
lot more people read it than you might think, even if they don't
directly invoke it.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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