Re: strftime() using '-' to remove leading 0s functionality removed or broken?

[Ed Morton]

Arnold - Yeah I don’t blame you. You could spend your life trying to keep up 
with things outside of your control and there’s definitely a strong argument 
for “if you’re using something that’s not documented then you’re on your own”. 
Thanks for taking a look.

Ed Morton

> On Jan 27, 2024, at 1:06 PM, arnold@skeeve.com wrote:
> 
> Hi Ed.
> 
> It's definitely an issue with the underlying C library version of
> strftime, which is what gawk uses.
> 
> I'll take a look at the manual, but I'm not sure I want to
> get into details like '-' flags which are unportable.
> 
> Thanks,
> 
> Arnold
> 
> Ed Morton <mortoneccc@comcast.net> wrote:
> 
>> Apparently the person for whom the `-` works in gawk 4.2.1 also sees it 
>> working in gawk 5.3.0, see:
>> 
>>    https://imgur.com/a/YtgCkA6
>> 
>> They are testing on a Mac while I tested on 2 different laptops, both 
>> running Windows 11, one in cygwin and the other git bash, so I'm 
>> guessing this is something to do with underlying primitives. It's odd to 
>> me  that `date` behaves differently from `gawk` in this regard but I 
>> guess it's just implemented differently. FWIW perl behaves the same way 
>> as gawk:
>> 
>>    $ cat tst.prl
>>    #!/usr/bin/perl
>>    use POSIX qw(strftime);
>> 
>>    # Modules used
>>    use strict;
>>    use warnings;
>> 
>>    # Print function
>>    printf("Without -: %s\n", strftime "%m", localtime);
>>    printf("With -:%s\n", strftime "%-m", localtime);
>> 
>>    $ ./tst.prl
>>    Without -: 01
>>    With -:
>>    $
>> 
>> and so does python:
>> 
>>    $ cat tst.py
>>    #!/usr/bin/python
>>    from datetime import datetime
>> 
>>    now = datetime.now()
>> 
>>    print("Without -:", now.strftime("%m"))
>>    print("With -:", now.strftime("%-m"))
>> 
>>    $ ./tst.py
>>    Without -: 01
>>    With -:
>> 
>> Assuming it's not something that can/should be made to work portably, 
>> maybe it's worth a brief note in the documentation that this is a thing, 
>> just like the underlying primitives impact on rounding and reading 
>> binary files are described elsewhere in the docs?
>> 
>>     Ed.
>> 
>>> On 1/27/2024 6:56 AM, Ed Morton wrote:
>>> Someone posted an answer at 
>>> https://stackoverflow.com/a/77884684/1745001 that puts a `-` in front 
>>> of `strftime()` format specifiers to remove leading `0`s so that, for 
>>> example, we can print the month number by doing:
>>> 
>>>    awk 'BEGIN{print strftime("%-m")}'
>>> 
>>> and get `1` output instead of the `01` we'd get with
>>> 
>>>    awk 'BEGIN{print strftime("%m")}'
>>> 
>>> That's consistent with how GNU date (and apparently various other 
>>> tools) works:
>>> 
>>>    $ date +'%-m'
>>>    1
>>>    $
>>> 
>>>    $ date +'%m'
>>>    01
>>>    $
>>> 
>>> and it's what that SO answer shows with gawk 4.2.1.
>>> 
>>> When I try to do the same with gawk 5.0.0 or later, though, then I get:
>>> 
>>>    $ awk 'BEGIN{print strftime("%-m")}'
>>> 
>>>    $
>>> 
>>>    $ awk 'BEGIN{print strftime("%m")}'
>>>    01
>>>    $
>>> 
>>> i.e. adding the `-` makes `strftime()` produce no output.
>>> 
>>> That functionality isn't documented in the manual best I can tell - is 
>>> that functionality that was removed or is it breakage or something else?
>>> 
>>>     Ed.