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

[arnold]

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.