NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/misc-part2/10664

Internet Message Format | 1996-08-05 | 5.5 KB

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From: [e-mail] (Peter Janes)
Newsgroups: comp.sys.amiga.misc
Subject: Re: AmigaOS 4.x features
Date: Sun, 31 Mar 96 22:26:35 EDT
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On 30-Mar-96 18:29:55, Charlie Moody <[e-mail]> wrote:
> On 29 Mar 1996 09:57:46 GMT, Tony Leneis wrote:
>: In article <4jfm8i$[e-mail]>,

> It may be *as* powerful, but not moreso (and what the heck is 'UNIX
> globbing'?)

UNIX globbing is another term for UNIX pattern matching, though don't ask
me where the term came from.  It's similar to, but not the same as,
pattern matching via regular expressions (which seems to be what you're
looking for).  (Regular expressions are the most powerful form of pattern
matching, assuming there's a regular pattern to what you're matching,
which is what we're dealing with here.  Apologies to math/CS majors for
a recursive and somewhat imprecise definition, but it's been over a year
since I even *thought* about this stuff.)

>: >Not just '?' and '*', but also the bracketed ranging, a la 'mv
>: >fred-[a-z].pgm ram:'.

>:      You can do that now.  Have you ever *tried* it before?  For example:

>       [3.1-specific example removed]

AFAIK, it was *not* 3.1-specific, but works under V36+....  (Of course, I'm
running on a V40 system, so I can't verify the V37 behaviour.)

>: For example, "dir sys:(a|b|c|e)#?".

> [additional references to documentation for more counter-intuitive,]
> [anti-logical methods deleted]

>               dir sys:[a-e]*

> Logical, simple, fast:  elegant.

And not a regular expression--that command, if interpreted correctly,
would list *all* of the files on sys:.  (The Kleene star represents 0 or
more occurrences of the term preceding it.)  The regexp form (taking into
account [] vs () translation) would be
    dir sys:[a-e].*

And it's not the same as the given example.  Your command includes files
beginning with D, as well.  (BTW, your command works as desired under
AmigaOS--in fact, I just did it.)  Under globbing, the example would be
    dir sys:[a-c|e]*
(which also works under AmigaOS).

>: I'd certainly take the functionality of the # operator any day
>: over the UNIX * operator (provided I've got a match-any-character operator
>: to go with it.)

> You'd gladly throw away the match-any-character option, provided you've
> got a match-any-character option to replace it???

There are other uses for #; most UN*X-style commands only do globbing, not
regexp, in my experience, so you can't say 'rm ab*c' to remove 'abbc' but
not 'abdc'.  To do this under AmigaOS, 'del a#bc'.

There are advantages and disadvantages to both regexps and AmigaOS pattern
matching.  I've had enough theoretical math and computer science to know what
regular expressions can and can't do, and that they're often less than
intuitive.

In case it hasn't been mentioned, one of the reasons * isn't activated by
default is that it was also chosen to refer to the console (and as the
escape character).  Assuming it is activated, doing 'dir *' won't give you
a directory of all files, but will produce an error message.  'dir **' will
work properly.  The former behaviour is for compatibility reasons--how do
you tell whether the user is referring to all files or to the console?  The
latter escapes the special meaning of '*-as-console' so that it's read as
'*-as-pattern'.  (Of course, that leads to why * was used as escape instead
of \, and why \ can't be used to continue lines, and why ; is the comment
character instead of the command separator, and why Ctrl-J is the command
separator....)

I was about to write that the biggest problem I've had using AmigaOS pattern
matching is that parentheses can't be nested, but decided to try:
    list ram:(*i(p|t)*)
on the following directory:
    Directory "ram:" on Sunday 31-Mar-96
    Disk.info                   1179 ----rw-d Today     17:50:59
    Clipboards                   Dir ----rwed Today     17:50:40
    T                            Dir ----rwed Today     19:55:48
    1 file - 2 directories - 7 blocks used
As expected, it produces:
    Directory "ram:" on Sunday 31-Mar-96
    Clipboards                   Dir ----rwed Today     17:50:40
    1 directory - 2 blocks used
Similarly,
    list ram:(*i~(p|t)*)
produces:
    Directory "ram:" on Sunday 31-Mar-96
    Disk.info                   1179 ----rw-d Today     17:50:59
    1 file - 3 blocks used

The latter, using globbing, would be something like:
    list ram:*i~[a-o|q-s|u-z]*

This was never meant to become an exhaustive list of globbing, regexp or
AmigaOS pattern matching capabilities, although it seems to have done so. 8^)
Suffice to say, they're different systems.  I believe the Amiga's is more
flexible, simply because it *includes* globbing syntax (including *, although
it's not enabled by default), it includes a slightly modified regexp syntax
(# for .), and it's easier to use, IMHO.

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