Gerald Pfeifer <gerald@pfeifer.com> writes:

> Hi Arsen,
>
> On Fri, 14 Apr 2023, Arsen Arsenović wrote:
>>> Did you intentionally not implement the following part of my suggestion
>>>
>>>    if [ x${MAKEINFO}x = xx ]; then
>>>    :
>> > that is, allowing to override from the command-line (or crontab)?
>> (answering both the questions)
>> 
>> This := operator is a handy "default assign" operator.  It's a bit of an
>> oddity of the POSIX shell, but it works well.  The line:
>> 
>>   : "${foo:=bar}"
>> 
>> is a convenient way of spelling "if foo is unset or null, set it to
>> bar".  the initial ':' there serves to discard the result of this
>> evaluation (so that only its side effect of updating foo if necessary is
>> kept)
>
> I understand, just am wondering whether and why the : is required? I 
> don't think we are using this construct anywhere else?

Without them, this would happen:

  ~$ "${foo:=foo}"
  bash: foo: command not found
  ~ 127 $ unset foo
  ~$ echo "${foo:=foo}"
  foo
  ~$ 

> (I was aware of the ${foo:=bar} syntax, just caught up by you pushing
> that part of the logic to the lowest level whereas I had it at the top
> level. That's purely on me.)
>
> Please go ahead and push this (or a variant without the : commands) and
> I'll then pick it up from there.

Thank you!  Hopefully we get this just in time for 13 :)

Pushed.
-- 
Arsen Arsenović