Re: regexp question
> I seem to be missing a piece of the puzzleI want to define a character > class ([]) > with atoms to (not) match involve negative look-ahead assertions.but no > joy. > > I am reading a stream of text that may contain the two segments \\n and \" > > I want to define a regexp that will match up to the first of either of > these.
I would suggest a slightly different approach, especially since you apparently might not have either sequence. Try
if ($str =~ /n|\\"/)
{
$mytext = substr($str, 0, $-[0]);
# do whatever with $mytext
}
The arrays @- and @+ contain the starting and ending offsets within a string of the portion successfully matched by a regular _expression_; the 0th elements refer to the whole regex, and other elements to the portions captured by parentheses.
See perlvar in the docs and the description of substr under perlfunc.
--Eric AmickColumbia, MD
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RE: regexp question
Hello all,
Thank you for the time. I guess that this foray into lookaround assertions
was bust. ;0) I am using Parse::RecDescent and I realized that I could use
the
order of Rules to ensure that if I *wasn't* looking at either a \\n or a \"
then I would have a bare \ that a simple Production could deal with.
Thanks (Mr $) to all!
chahn
-Original Message-
From: $Bill Luebkert [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 14, 2004 7:37 PM
To: Christopher Hahn
Cc: [EMAIL PROTECTED]
Subject: Re: regexp question
Christopher Hahn wrote:
> $Bill,
>
> The (?: ) construct may be non-capturing, but it does eat text from
> the buffer (sic)
>
> ...and, besides, when I ran it I saw this:
> =
> 1: asd asdf adf asd \n asd adf
> 2: asd asdf adf asd \n asd adf
> 3: asd asdf adf asd asd adf
> =
>
> where I need to see something like this:
> =
> 1: asd asdf adf asd
> 2: asd asdf adf asd \n asd adf
> 3: asd asdf adf asd asd adf
> 4: asd asdf adf asd asd adf " ad dasf \n dsaf
> =
>
> i.e. \n should pass through, where \\n or \" should not.
Does a non-greedy match help (also - I was missing an escape or two on the
\\n):
foreach (
'1: asd asdf adf asd n asd adf \" ad dasf dsaf ',
'2: asd asdf adf asd \n asd adf \" ad dasf dsaf ',
'3: asd asdf adf asd asd adf \" ad dasf n dsaf ',
'4: asd asdf adf asd asd adf " ad dasf \n dsaf ',
) {
if (/^(.*?)(?:n|\\")/) {
print "$1\n";
}
}
>
> What about trying something like:
>
> $strval =~ m/^(( [^\\] | \\ (?! \\ (?= n)) | \\ (?! \") )*)/x;
>
> which (or so I think ;0) collects as many characters from the
> beginning of $str that meet these conditions (bs = backslash):
> =
>1) not a bs
> or 2) a bs that is *not* followed by a ( bs that *is* followed by a n
> ) or 3) a bs that is *not* followed by a "
> =
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Re: regexp question
Christopher Hahn wrote:
> $Bill,
>
> The (?: ) construct may be non-capturing, but it does eat text from the
> buffer (sic)
>
> ...and, besides, when I ran it I saw this:
> =
> 1: asd asdf adf asd \n asd adf
> 2: asd asdf adf asd \n asd adf
> 3: asd asdf adf asd asd adf
> =
>
> where I need to see something like this:
> =
> 1: asd asdf adf asd
> 2: asd asdf adf asd \n asd adf
> 3: asd asdf adf asd asd adf
> 4: asd asdf adf asd asd adf " ad dasf \n dsaf
> =
>
> i.e. \n should pass through, where \\n or \" should not.
Does a non-greedy match help (also - I was missing an escape
or two on the \\n):
foreach (
'1: asd asdf adf asd n asd adf \" ad dasf dsaf ',
'2: asd asdf adf asd \n asd adf \" ad dasf dsaf ',
'3: asd asdf adf asd asd adf \" ad dasf n dsaf ',
'4: asd asdf adf asd asd adf " ad dasf \n dsaf ',
) {
if (/^(.*?)(?:n|\\")/) {
print "$1\n";
}
}
>
> What about trying something like:
>
> $strval =~ m/^(( [^\\] | \\ (?! \\ (?= n)) | \\ (?! \") )*)/x;
>
> which (or so I think ;0) collects as many characters from the beginning of
> $str that
> meet these conditions (bs = backslash):
> =
>1) not a bs
> or 2) a bs that is *not* followed by a ( bs that *is* followed by a n )
> or 3) a bs that is *not* followed by a "
> =
--
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RE: regexp question
$Bill,
The (?: ) construct may be non-capturing, but it does eat text from the
buffer (sic)
...and, besides, when I ran it I saw this:
=
1: asd asdf adf asd \n asd adf
2: asd asdf adf asd \n asd adf
3: asd asdf adf asd asd adf
=
where I need to see something like this:
=
1: asd asdf adf asd
2: asd asdf adf asd \n asd adf
3: asd asdf adf asd asd adf
4: asd asdf adf asd asd adf " ad dasf \n dsaf
=
i.e. \n should pass through, where \\n or \" should not.
What about trying something like:
$strval =~ m/^(( [^\\] | \\ (?! \\ (?= n)) | \\ (?! \") )*)/x;
which (or so I think ;0) collects as many characters from the beginning of
$str that
meet these conditions (bs = backslash):
=
1) not a bs
or 2) a bs that is *not* followed by a ( bs that *is* followed by a n )
or 3) a bs that is *not* followed by a "
=
Am I making any sense? ;0)
Thank you for taking the time in any case!
Christopher
-Original Message-
From: $Bill Luebkert [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 14, 2004 1:41 PM
To: Christopher Hahn
Cc: [EMAIL PROTECTED]
Subject: Re: regexp question
Christopher Hahn wrote:
> Hey,
>
> I seem to be missing a piece of the puzzleI want to define a
> character class ([]) with atoms to (not) match involve negative
> look-ahead assertions.but no joy.
>
> I am reading a stream of text that may contain the two segments \\n and \"
>
> I want to define a regexp that will match up to the first of either of
> these.
>
> ...ie. something like ([^]*) where the character class is just the two
> sequences above.
>
> ...but they are not characters at all, but strings, and so I wonder
> how to approach this.
>
> Question: how best to do something to set
>
>$1 == every character in the string up to and not including the
> first of either a \\n or a \"
>
> That is all. (something like $strval =~ m/ (.* (?! \\ (?= \" | \\ (?=
> n) ) )
> )/x;)
>
> I am going to use this regexp in a Parse::RecDescent Production, and
> have other Rules to deal with the \\n and \" strings.
>
> I am banging on this and will report when something good comes out of
> it, but please do chime in with any "best practices" that suggest
> themselves to you.
I assume that \\n is actually 3 characters and not a newline.
It should be as simple as :
use strict;
foreach (
'1: asd asdf adf asd \\n asd adf \" ad dasf dsaf ',
'2: asd asdf adf asd \n asd adf \" ad dasf dsaf ',
'3: asd asdf adf asd asd adf \" ad dasf \\n dsaf ',
'4: asd asdf adf asd asd adf " ad dasf \n dsaf ',
) {
if (/^(.*)(?:n|\\")/) {
print "$1\n";
}
}
__END__
--
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/ ) /--< o // // Castle of Medieval Myth & Magic
http://www.todbe.com/
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Re: regexp question
Christopher Hahn wrote:
> Hey,
>
> I seem to be missing a piece of the puzzleI want to define a character
> class ([])
> with atoms to (not) match involve negative look-ahead assertions.but no
> joy.
>
> I am reading a stream of text that may contain the two segments \\n and \"
>
> I want to define a regexp that will match up to the first of either of
> these.
>
> ...ie. something like ([^]*) where the character class is just the two
> sequences above.
>
> ...but they are not characters at all, but strings, and so I wonder how to
> approach this.
>
> Question: how best to do something to set
>
>$1 == every character in the string up to and not including the first of
> either a \\n or a \"
>
> That is all. (something like $strval =~ m/ (.* (?! \\ (?= \" | \\ (?= n) ) )
> )/x;)
>
> I am going to use this regexp in a Parse::RecDescent Production, and have
> other Rules to
> deal with the \\n and \" strings.
>
> I am banging on this and will report when something good comes out of it,
> but please do
> chime in with any "best practices" that suggest themselves to you.
I assume that \\n is actually 3 characters and not a newline.
It should be as simple as :
use strict;
foreach (
'1: asd asdf adf asd \\n asd adf \" ad dasf dsaf ',
'2: asd asdf adf asd \n asd adf \" ad dasf dsaf ',
'3: asd asdf adf asd asd adf \" ad dasf \\n dsaf ',
'4: asd asdf adf asd asd adf " ad dasf \n dsaf ',
) {
if (/^(.*)(?:n|\\")/) {
print "$1\n";
}
}
__END__
--
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/ ) /--< o // // Castle of Medieval Myth & Magic http://www.todbe.com/
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regexp question
Hey, I seem to be missing a piece of the puzzleI want to define a character class ([]) with atoms to (not) match involve negative look-ahead assertions.but no joy. I am reading a stream of text that may contain the two segments \\n and \" I want to define a regexp that will match up to the first of either of these. ...ie. something like ([^]*) where the character class is just the two sequences above. ...but they are not characters at all, but strings, and so I wonder how to approach this. Question: how best to do something to set $1 == every character in the string up to and not including the first of either a \\n or a \" That is all. (something like $strval =~ m/ (.* (?! \\ (?= \" | \\ (?= n) ) ) )/x;) I am going to use this regexp in a Parse::RecDescent Production, and have other Rules to deal with the \\n and \" strings. I am banging on this and will report when something good comes out of it, but please do chime in with any "best practices" that suggest themselves to you. TIA! Christopher -- Realisant mon espoir, je me lance vers la gloire Christopher Kenneth Hahn -- [EMAIL PROTECTED] ___ Perl-Win32-Users mailing list [EMAIL PROTECTED] To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
Re: RegExp Question
John Giordano wrote:
> $grep_deferred = system ('findstr DeferredStatus response1');
>
> print "$grep_deferred\n\n";
[snip]
> $grep_deferred has this in it:
>
> src="/images/btnstats.gif" width=120 height=40 border=0 alt="Mail
> Status">
Are you sure? Try printing out "bloop\nblip\n$grep_deferred\nblep\n" and see
whether this line comes between "blip" and "blep".
>From `perldoc -f system`:
The return value is the exit status of the program as returned
by the `wait' call. To get the actual exit value divide by 256.
So if $grep_deferred is the return value from system, it's probably a
number. The line you're seeing on the screen is presumably the output of
findstr, which went to STDOUT; since you didn't redirect STDOUT, it went the
same place your print went.
You probably want `` (backticks).
ObTMTOWTDI: if you're looking for a fixed substring such as ' sub { $a = index '', ' sub { $a = index '[a
href="/c9410ee04de9845704db8951dfde015b/DeferredStatus">', ' sub { $a = '' =~ / sub { $a = '[a
href="/c9410ee04de9845704db8951dfde015b/DeferredStatus">' =~ / sub { $a = index 'fhuhge8a goija fgoja w04gua
roigj oöijf g9a8u onigö lfsdkj gölija osij ga0 jügojar öoigj öosijd ü08g9u
gaji fäöigjah+w r0g9j aäüjäfpoiajs öoijfd +ajsd fäüpioaj öwoeijf öoasuidhf
p9iawh üefhaj woeijg awopihg apiuehrg üaiowj eoöfigjaw ejif', ' sub { $a = index 'fhuhge8a goija fgoja w04gua
roigj oöijf g9a8u onigö lfsdkj gölija osij ga0 jügojar öoigj öosijd ü08g9u
gaji fäöigjah+w r0g9j aäüjäfpoiajs öoijfd +ajsd fäüpioaj öwoeijf öoasuidhf
p9iawh üefhaj woeijg awopihg apiuehrg üaiowj eoöfigjaw ejif[a
href="/c9410ee04de9845704db8951dfde015b/DeferredStatus">', ' sub { $a = 'fhuhge8a goija fgoja w04gua roigj
oöijf g9a8u onigö lfsdkj gölija osij ga0 jügojar öoigj öosijd ü08g9u gaji
fäöigjah+w r0g9j aäüjäfpoiajs öoijfd +ajsd fäüpioaj öwoeijf öoasuidhf p9iawh
üefhaj woeijg awopihg apiuehrg üaiowj eoöfigjaw ejif' =~ / sub { $a = 'fhuhge8a goija fgoja w04gua roigj
oöijf g9a8u onigö lfsdkj gölija osij ga0 jügojar öoigj öosijd ü08g9u gaji
fäöigjah+w r0g9j aäüjäfpoiajs öoijfd +ajsd fäüpioaj öwoeijf öoasuidhf p9iawh
üefhaj woeijg awopihg apiuehrg üaiowj eoöfigjaw ejif[a
href="/c9410ee04de9845704db8951dfde015b/DeferredStatus">' =~ / sub { $a = 1; },
});
__END__
Output:
Benchmark: timing 500 iterations of assign, index.end.found,
index.end.notfound, index.start.found, inde
x.start.notfound, regex.end.found, regex.end.notfound, regex.start.found,
regex.start.notfound...
assign: 0 wallclock secs ( 1.02 usr + 0.00 sys = 1.02 CPU) @
4897159.65/s (n=500)
index.end.found: 9 wallclock secs ( 9.79 usr + 0.00 sys = 9.79 CPU) @
510516.64/s (n=500)
index.end.notfound: 12 wallclock secs (12.38 usr + 0.00 sys = 12.38 CPU) @
404007.76/s (n=500)
index.start.found: 3 wallclock secs ( 2.49 usr + 0.00 sys = 2.49 CPU) @
2004811.55/s (n=500)
index.start.notfound: 5 wallclock secs ( 5.42 usr + 0.00 sys = 5.42 CPU)
@ 922849.76/s (n=500)
regex.end.found: 12 wallclock secs (11.42 usr + 0.00 sys = 11.42 CPU) @
437943.42/s (n=500)
regex.end.notfound: 13 wallclock secs (13.34 usr + 0.00 sys = 13.34 CPU) @
374840.69/s (n=500)
regex.start.found: 5 wallclock secs ( 3.91 usr + 0.00 sys = 3.91 CPU) @
1280081.93/s (n=500)
regex.start.notfound: 7 wallclock secs ( 6.38 usr + 0.00 sys = 6.38 CPU)
@ 783821.92/s (n=500)
Rate regex.end.notfound index.end.notfound
regex.end.found index.end.found regex.start.notfound index.start.notfound
regex.start.found index.start.found assign
regex.end.notfound374841/s ---7%
-14%-27% -52% -59% -71%
-81% -92%
index.end.notfound404008/s 8% --
-8%-21% -48% -56% -68%
-80% -92%
regex.end.found 437943/s17% 8%
---14% -44% -53% -66%
-78% -91%
index.end.found 510517/s36%26%
17% -- -35% -45% -60%
-75% -90%
regex.start.notfound 783822/s 109%94%
79% 54% -- -15% -39%
-61% -84%
index.start.notfound 922850/s 146% 128%
111% 81% 18% -- -28%
-54% -81%
regex.start.found1280082/s 242% 217%
192%151% 63% 39%--
-36% -74%
index.start.found2004812/s 435% 396%
358%293% 156% 117% 57%
-- -59%
assign 4897160/s 1206% 1112%
1018%859% 525% 431% 283%
144% --
___
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Re: RegExp Question
John Giordano wrote:
>
> Hello,
>
> Could someone please tell me why this:
>
> ###
> $grep_deferred = system ('findstr DeferredStatus response1');
>
> print "$grep_deferred\n\n";
>
> if ($grep_deferred =~ /
> print "It contains } else {
>
> print "It doesn't contain }
> -
> doesn't find this:
>
>
> The above code may need some further explanation. I am trying to extract
> the
> $grep_deferred has this in it:
>
> src="/images/btnstats.gif" width=120 height=40 border=0 alt="Mail
> Status">
>
> < doesn't need a backslash in front of it right?
Correct, it doesn't. This test snippet works fine for me (I modified
your RE, but it works your way too):
use strict;
my $grep_deferred =
q{} .
q{};
print "$grep_deferred\n\n";
if ($grep_deferred =~ /http://www.todbe.com/
/ ) /--< o // // Mailto:[EMAIL PROTECTED] http://dbecoll.webjump.com/
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