No, the problem is not an understanding of how REXX evaluates expressions.
The problem is that EXECIO is one of the few places that a variable NAME
is an operand, not the variable CONTENTS.
Tony Thigpen
Seymour J Metz wrote on 6/5/20 2:11 PM:
Your statement implies that "sometimes" it is legitimate to not use quotes.
In fact, sometimes it is mandatory to not use them.
Your suggested wording has the same issue as what is in the manual; it
prescribes rules that aren't always appropriate. The REXX Reference manual has
a perfectly adequate description of how REXX evaluates expressions: refer the
reader to that. Don't invent rules that sometimes don't apply.
The root problem is that someone is writing code without understanding the
language.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
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From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of
Tony Thigpen [t...@vse2pdf.com]
Sent: Friday, June 5, 2020 2:03 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Gratuitous EXECIO Documentation
Sorry, but I disagree.
Your statement implies that "sometimes" it is legitimate to not use
quotes. I would say that "sometimes you can get lucky and get away with
not using quotes". :-)
A very basic documentation statement would be:
Some formats of the EXECIO command may reference a variable
by the name of the variable. Such references should be
within quoted text. Such an example is the variable name
of a stem variable:
Correct:
'EXECIO 5 DISKW' ddname '(STEM MYSTEM.'
Incorrect:
'EXECIO 5 DISKW' ddname '(STEM' mystem.
Use without quotes can result in unpredictable results.
I really think this is the root problem, not the fact that someone
defined a variable with the same name as a common keyword, such as your
example with "STEM". Such an example is just part of the language
restriction and not directly related to EXECIO.
Tony Thigpen
Seymour J Metz wrote on 6/5/20 12:56 PM:
My problem with gratuitous documentation is that they invariably get it wrong.
Describe the actual requirements and direct the reader to the appropriate
places for details. In this case, something like:
As with any command issued to an external environment, ensure that the
expression you use evaluates to the intended EXECIO command. In
particular, it may be prudent to always quote keywords to avoid
confusion with variables with the same name. For example, if you assign
the variable "stem" to a value other than 'STEM' and then use
EXECIO 5 DISKW ddname '(' STEM
instead of
EXECIO 5 DISKW ddname '( STEM'
in your code, you will not invoke the correct command.
Would be reasonable if they have to spell it out.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of
Paul Gilmartin [0000000433f07816-dmarc-requ...@listserv.ua.edu]
Sent: Friday, June 5, 2020 11:29 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Gratuitous EXECIO Documentation
In:
https://www.ibm.com/support/knowledgecenter/SSLTBW_2.3.0/com.ibm.zos.v2r3.ikja300/dup0037.htm
I see the verbiage:
When you use EXECIO, you must ensure that you use quotation marks
around any operands, such as DISKW, STEM, FINIS, or LIFO. Using
quotation marks prevents the possibility of the operands being substituted
as variables. For example, if you assign the variable stem to a value in
the exec and then issue EXECIO with the STEM option, if STEM is not
enclosed in quotation marks, it is substituted with its assigned value.
Sheesh! A similar caution might be included for any command in the Ref.,
but it doesn't belong.
"must ensure"? Well, not always.
I infer the etiology: A troublesome user once coded:
STEM=SKIP /* perhaps */
EXECIO ...
... got astonishing results; went to SR; got fully proper "REJ; RTFM";
vindictively submitted RCF. A feckless tech writer acceded and added
the paragraph.
I strongly suspect the matter is covered properly earlier (citation needed)
in the Ref., which shouldn't be cluttered with such errant rubbish.
(I was reading that Ref. to see whether EXECIO assembles segments
of V[B]S records. Didn't find it.)
-- gil
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