Re: Awk error

Charles Calvert wrote:
> Since we're engaging in a little friendly pedantry...

:-)

> On 10/27/2009 6:30 AM, Keith MARSHALL wrote:
>
> [attributions added back in]

This utterly abysmal mail client, which my employer insists I use, messes
them up horrendously; sorry about that.

>> On 10/23/2009 10:56 AM, Charles Calvert wrote:
>
>>> On 10/23/2009 10:31 AM, [email protected] wrote:
>>
>>>> I can't seem to get awk to work.
>>>> Here is the command line I'm trying to use:
>>>>
>>>> svn ls -R | awk "print $1"
>>> Try:
>>>
>>>            svn ls -R | awk "{print $1}"
>>>
>>> The default rule must be enclosed in braces.
>>
>> Actually, this is not strictly so; while your suggested remedy
>> is correct in this instance, your explanation is wrong.
>>
>> An awk "rule", (usually called a "statement",
>
> Most of my understanding of awk comes from "Effective awk Programming"
> and "sed & awk" in which Mr. Robbins tends to use the word "rule" rather
> than the word "statement", so I think that "usually" depends on the
> context.  I would agree that "statement" has a more well defined meaning
> in a programming context, but plenty of programming languages have their
> little variations on terminology.

I didn't mean to impugn your use of the word "rule"; just introducing
what I believe to be the more common terminology, esp. in the formal
documentation of awk, (where, FTR, my "match-criterion" is usually
referred to as a "pattern"; see:
   http://www.opengroup.org/onlinepubs/009695399/utilities/awk.html ).

>> for it is a part
>> of an awk "script" which itself comprises one or more of such
>> statements), comprises two parts:
>>
>>       match-criterion { action [; ...] }
>>
>> It's the *action* part of the statement which must be enclosed
>> in braces, and this applies to *all* statements;
>
> I did not imply the opposite.  Brad failed to enclose the action in
> braces and I stated that he needed to do so.

Exactly so; your suggested remedy was correct, as I said.  However...

>  I don't see how one can
> reasonably conclude that this implies that braces should not enclose
> any other action.  Perhaps I have misunderstood your use of emphasis
> in this case?

I thought your wording may have been potentially confusing; you stated
that "the default *rule* must be enclosed in braces" (my emphasis), but
if we accept, in your terminology, that "rule" is synonymous with the
"statement" of mine, then that would be incorrect: it is only the
*action* part of the "rule" which must be enclosed in braces, (and
there really isn't any realistic concept of a "default rule"; the awk
language specification allows *either* the pattern or the action to be
defaulted, but never both in the same statement).

>> (in fact, if any statement is given at all, there is no applicable
>> concept of a "default"; any statement may omit either the
>> match-criterion part, which then defaults to matching *every* input
>> line, or it may omit the action part, which then defaults to echoing
>> the entire matched input line to the output stream.
>
> I should have said the "empty pattern"[1], but my mind came up with
> "default" instead.

Ah!  With that qualification, your analysis becomes correct, if not as
clearly expressed as it might have been.

> Thanks for the clarification.

You're welcome.  I thought it necessary, to avoid possibly confusing an
OP who clearly isn't experienced in awk programming.

--

Regards,
Keith.
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