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Re: manpage error-Arithmetic Evaluation of numbers with explicit base

From: Thomas Bartosik
Subject: Re: manpage error-Arithmetic Evaluation of numbers with explicit base
Date: Mon, 29 Mar 2010 15:50:20 +0200

Don't get me wrong, I am a full time bash script programmer and I do know how 
man pages (and their syntax) look like. I use this syntax myself in every 
usage() I write...
Still I think it is misleading.

I simply cannot see how a newb can tell the difference between a bracket that's 
part of the syntax:
[...]Any  element  of  an array may be referenced using ${name[subscript]}.[...]

.. and one that's not:
[...]Constants with a leading 0 are interpreted as octal numbers.  A  leading 
0x or 0X denotes hexadecimal.  Otherwise,  numbers  take  the  form [base#]n,  
where  base  is a decimal number between 2 and 64 representing the arithmetic 
base, and n is a number in that base. If base# is omitted, then base 10 is 

Granted, it states that base# can be omitted, but I still cannot tell why it is 
an "optional" indicator here and "part of the syntax" with the array 
explanation. (where it basically can be left out as well to get just the first 
element, so it isn't mandatory). It could be part of the syntax here equally 
well in my understanding..

But things get even more complicated with array assignments:
[...]Arrays are assigned to using compound assignments of the form name=(value1 
... valuen), where each value is of the form [subscript]=string. Indexed array 
assignments do not require the bracket and subscript. When assigning to indexed 
arrays, if the optional  brackets  and  subscript  are supplied, that index is 
assigned to[...]

If everything in brackets is optional it should be [subscript=]string or the 
value will be a literal "=string" if the optional [subscript] gets left out...

Please don't get me wrong. I have no problem in understanding the man page this 
way, but I do think it is inconsistent. And I absolutely understand why, as 
there are multiple meanings for a poor little bracket ;->

On Mon, 03/29, 2010 02:51:18PM, Greg Wooledge wrote:

> On Mon, Mar 29, 2010 at 02:22:35PM +0200, Thomas Bartosik wrote:
> > Well OK, I understand. Still I think there should be a difference in the
> man
> > page when it comes to brackets. When talking about arrays, the brackets
> are
> > NOT an option but mandatory.
> That's correct.  Referencing a specific element of an array by index
> uses square brackets as part of the syntax.
> > (and it might be me being uneducated, but how to you print out the
> decimal equivalent of binary 11 without using brackets? I can only produce the
> correct value "3" by
> > echo $[2#11]
> The $((...)) notation is preferred and documented.
> echo $((2#11))
> > The "optional" refers to being able to not use it when operating on a
> normal
> > decimal number as I understand this now. Then where can I find that I
> have to
> > use brackets like I use them -- which only is a side effect of the
> brackets I
> > have seen in the man page and seems unrelated on the whole!)
> You are confusing literal square brackets which are part of the syntax
> of a command (as in array indexing) with the brackets used in man pages
> and other documents to indicate that something is optional.
> We're not saying that literal square brackets are optional when doing
> array indexing.  We're saying that the things INSIDE brackets in a man
> page are optional -- and that the brackets themselves are NOT part of
> the command at all, but rather, part of the documentation.
> I understand how it's easy to get confused by that, but eventually
> you'll have to get used to it.
> Look at ls(1) from Debian as an example:
>        ls [OPTION]... [FILE]...
> Or from HP-UX:
>        ls [-abcdefgilmnopqrstuxACFLR1] [names]
> Or from OpenBSD:
>      ls [-1AaCcdFfghikLlmnopqRrSsTtux] [file ...]
> See the brackets there?  They indicate that the options and filenames
> are optional.  They don't mean that you type literal square brackets
> around the options and filenames.

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