What does this reg expression mean?

[Lyn]

I'm trying to get my head around regular expressions while
maintaining some semblance of sanity. I'm canabalising a
similar program to construct my own, and it keeps using an
expression I'm not familiar with as a pattern matcher.

It looks like this:

([^"]*)

To me, it looks like 0 or more occurences of the beginning of
a string or quote character, but that doesn't make much sense
in the context it's used. And it's used multiple times, so
I'm hoping it's a widely used trick that someone might be able
to explain to me?

Cheers,
Lyn

[view_as_html]

Re: What does this reg expression mean?

^ is the anchor here is a a good explanation on that

http://www.anaesthetist.com/mnm/perl/regex.htm

Lyn wrote:
[color=blue]
> I'm trying to get my head around regular expressions while
> maintaining some semblance of sanity. I'm canabalising a
> similar program to construct my own, and it keeps using an
> expression I'm not familiar with as a pattern matcher.[/color]
[color=blue]
> It looks like this:[/color]
[color=blue]
> ([^"]*)[/color]
[color=blue]
> To me, it looks like 0 or more occurences of the beginning of
> a string or quote character, but that doesn't make much sense
> in the context it's used. And it's used multiple times, so
> I'm hoping it's a widely used trick that someone might be able
> to explain to me?[/color]
[color=blue]
> Cheers,
> Lyn[/color]

[Jürgen Exner]

Re: What does this reg expression mean?

Lyn wrote:
[...][color=blue]
> It looks like this:
>
> ([^"]*)
>
> To me, it looks like 0 or more occurences of the beginning of
> a string or quote character, but that doesn't make much sense
> in the context it's used. And it's used multiple times, so
> I'm hoping it's a widely used trick that someone might be able
> to explain to me?[/color]

Inside of a character class the caret "^" looses it's special meaning and
does not match beginning of the string any more.
So this RE matches any sequence of consecutive carets and double quotes.

jue

[magoo]

Re: What does this reg expression mean?

In article <4%6mc.88856$G_ .75035@nwrddc02 .gnilink.net>,
jurgenex@hotmai l.com says...[color=blue]
> Lyn wrote:
> [...][color=green]
> > It looks like this:
> >
> > ([^"]*)
> >
> > To me, it looks like 0 or more occurences of the beginning of
> > a string or quote character, but that doesn't make much sense
> > in the context it's used. And it's used multiple times, so
> > I'm hoping it's a widely used trick that someone might be able
> > to explain to me?[/color]
>
> Inside of a character class the caret "^" looses it's special meaning and
> does not match beginning of the string any more.
> So this RE matches any sequence of consecutive carets and double quotes.
>
> jue
>
>
>[/color]
Jue,

Shame on you for this bit of misinformation!
From the "Regular Expression Pocket Reference" by Tony Stubblebine:

"Character classes are ways to define or specify a set of characters.
A character class matches one character in the input string that is
within the defined set.

Normal classes: [...] and [^...]
Character classes, [...], and negated character classes, [^...],
allow you to list the characters that you do or do not want to match.
(More info...)

So this RE, ([^"]*), captures zero or more occurrences of anything that
is not a double-quote. With the parentheses, there is capturing also
into a numbered variable, i.e., $1, $2 depending on how many previous
capturing parenthesis exist. Perhaps a better RE, in my mind, would be
([^"]+), i.e., one or more occurrences of anything not a double-quote.
The asterisk modifier would match zero or more of anything not a double-
quote which may or may not be what you want.

magoo

[Jürgen Exner]

Re: What does this reg expression mean?

magoo wrote:[color=blue]
> In article <4%6mc.88856$G_ .75035@nwrddc02 .gnilink.net>,
> jurgenex@hotmai l.com says...[color=green]
>> Inside of a character class the caret "^" looses it's special
>> meaning and does not match beginning of the string any more.[/color][/color]
[Wrong explanation snipped][color=blue]
>
> Shame on you for this bit of misinformation![/color]

Ooops, you are right, of course
[color=blue]
> From the "Regular Expression Pocket Reference" by Tony Stubblebine:[/color]

However, does this book describe Perl REs or other REs?
I would rather check the Perl documentation because REs differ quite a bit
for different languages.

jue

[Terry Michaels]

Re: What does this reg expression mean?


"Jürgen Exner" <jurgenex@hotma il.com> wrote in message
news:hEcmc.8900 2$G_.29787@nwrd dc02.gnilink.ne t...[color=blue]
> magoo wrote:[color=green]
> > In article <4%6mc.88856$G_ .75035@nwrddc02 .gnilink.net>,
> > jurgenex@hotmai l.com says...[color=darkred]
> >> Inside of a character class the caret "^" looses it's special
> >> meaning and does not match beginning of the string any more.[/color][/color]
> [Wrong explanation snipped][color=green]
> >
> > Shame on you for this bit of misinformation![/color]
>
> Ooops, you are right, of course
>[color=green]
> > From the "Regular Expression Pocket Reference" by Tony Stubblebine:[/color]
>
> However, does this book describe Perl REs or other REs?
> I would rather check the Perl documentation because REs differ quite a bit
> for different languages.
>
> jue
>
>[/color]

The book describes Perl RE's as well as others.
I don't have it in front of me, it is on my desk at work.
I just reached for the nearest reference I had at the time ;>)