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Reply-To: Brian DOT Inglis AT SystematicSw DOT ab DOT ca
Subject: Re: Cygwin strptime() is missing "%s" which strftime() has
To: cygwin AT cygwin DOT com
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From: Brian Inglis <Brian DOT Inglis AT SystematicSw DOT ab DOT ca>
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Date: Tue, 29 Aug 2017 18:25:08 -0600
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On 2017-07-25 10:47, Brian Inglis wrote:
> On 2017-07-24 17:18, Kaz Kylheku wrote:
>> On 24.07.2017 15:51, Brian Inglis wrote:
>>> On 2017-07-24 15:02, Hans-Bernhard Bröker wrote:
>>>> Am 24.07.2017 um 04:09 schrieb Lavrentiev, Anton (NIH/NLM/NCBI) [C]:
>>>>
>>>>> rather it's a question about portability of code that
>>>>> uses %s for both functions and expects it to work unchanged in the
>>>>> Cygwin environment.
>>>>
>>>> And the answer to that question is: such code _is_not_portable_, and therefore
>>>> that expectation is wrong.
>>>>
>>>> If that code claims to be portable, then its use of %s in either of those
>>>> functions constitutes a _bug_.
>>>>
>>>> In the old days there was a well-known fallacy known by the slogan "all the
>>>> world's a VAX."  Nowadays it appears to have been replaced by an equally
>>>> wide-spread, and equally incorrect belief that all the world is Linux.  Well,
>>>> it's not.  Not even the whole Un*x world is Linux.
>>>
>>> Rather "all the world's a GNU" i.e. glibc, but there's also BSD libc, RTEMS and
>>> Cygwin newlib, and others.
>>
>> Since the utilities depend on the C library functionality for strptime and
>> strftime, even having GNU utilities won't help.
>>
>> There doesn't appear any nice way in POSIX shell scripting to have access to
>> the seconds since the Epoch.
>>
>> If you have GNU Awk, it has some time functions like mktime, which don't rely
>> on any C library extensions.
> 
> If you have GNU gawk you probably also have GNU coreutils date, which supports
> +%s for output and -d AT nnnnnnnnnn for input, whether or not the system strftime
> and strptime support %s.
> 
> GNU coreutils date with shell arithmetic is adequate to support shell script
> conversions between time scales with different epochs e.g. Julian Day, Modified
> Julian Day, NTP, Unix, GPS, and calculations using those values.
> 
> Awk, JS, or some other language supporting FP is required for subsecond or
> fractional day accuracy with convenient output.

Patch in latest test release provides %s support for strptime(3) used by
strptime(1).
Another strptime(3) patch was just submitted to fix %F handling.
More newlib time patches coming to fix handling years around INT_MAX and high
values of time_t.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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