Capturing parens regexp in one line?

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Gurus,

I've not seen this done, so I don't know if it can be, but... Is there a
way to get $1 from a pair of parens in a regexp into a variable in one
line? That is...

my $foo = 'http://10.20.30.40/gargle';

$foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
my $fee = $1;

print "IP = \"$fee\"\n";

....is there some way to get the second and third lines into one line?

Deane Rothenmaier
Systems Architect
Walgreens Corp.
847-914-5150

"Science is not only compatible with spirituality; it is a profound source
of spirituality." -- Carl Sagan
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Gurus,



I've not seen this done, so I don't know if it can be, but...  Is there a way to get $1 from a pair of parens in a regexp into a variable in one line? That is...



  my $foo = 'http://10.20.30.40/gargle';

 

  $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;

  my $fee = $1;

 

  print "IP = \"$fee\"\n";



...is there some way to get the second and third lines into one line?



Deane Rothenmaier

Systems Architect

Walgreens Corp.

847-914-5150



"Science is not only compatible with spirituality; it is a profound source of spirituality." -- Carl Sagan
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Recent posts

I could be wrong, and I certainly do not want to discourage anyone from
seeking help, but I thought the general purpose of this listserv was to
discuss issues related to the ActiveState perl, not coding issue.
beginners@perl.org might be a better place for questions concerning coding
or use of perl. Beginners certainly has a higher volume and several
members usually respond to each post, and quickly at that.

Just a thought,

Kevin


Kevin Viel
PhD Candidate
Department of Epidemiology
Rollins School of Public Health
Emory University
Atlanta, GA 30322
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Re: Capturing parens regexp in one line?

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Hi,

my $foo =3D 'http://10.20.30.40/gargle';
my ($fee) =3D $foo =3D~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g;

Note the /g at the end.

Octavian

----- Original Message -----=20
From: Deane.Rothenmaier@walgreens.com=20
To: activeperl@listserv.ActiveState.com=20
Sent: Monday, January 08, 2007 9:45 PM
Subject: Capturing parens regexp in one line?



Gurus,=20

I've not seen this done, so I don't know if it can be, but... Is =
there a way to get $1 from a pair of parens in a regexp into a variable =
in one line? That is...=20

my $foo =3D 'http://10.20.30.40/gargle';=20
=20
$foo =3D~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;=20
my $fee =3D $1;=20
=20
print "IP =3D \"$fee\"\n";=20

...is there some way to get the second and third lines into one line?=20

Deane Rothenmaier
Systems Architect
Walgreens Corp.
847-914-5150

"Science is not only compatible with spirituality; it is a profound =
source of spirituality." -- Carl Sagan


------------------------------------------------------------ -------------=
-----


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Re: Capturing parens regexp in one line?

Deane grumbled:
> I've not seen this done, so I don't know if it can be, but... Is there
a way to get $1 from a pair of parens in a regexp into a variable in one
line? That is...
my $foo = 'http://10.20.30.40/gargle';

$foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
my $fee = $1;

print "IP = \"$fee\"\n";
> ..is there some way to get the second and third lines into one line?

Well - maybe. But
$foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
my $fee = $1;

is a Bad Thing, on its own. Did it match? You don't know. If it didn't,
there's the oft-overlooked issue w/ perl in that "$1" and the rest of the
capture vars retain their old values after a failed match. That is (note
the RE change to 3,3 for the first octet so it fails):
if ( $do_this =~ /(y)/ ) {
my $foo = 'http://10.20.30.40/gargle';
$foo =~ /(\d{3,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
my $fee = $1;
print "IP = \"$fee\"\n";

prints:
IP = "y"

You always want to test your matches. What you want to do is have the
match return a list of capture vars:
if ( my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/ ) {
print "IP = \"$fee\"\n";
}
else {
print "NO IP found in \"$foo\"\n";
} # if ( my ($fee) = $foo =~
/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/ )


You need the parens around "$fee" to make it into list context, the match
returns the list of capture vars. If you did:
if ( my $fee = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/ ) {

that is, scalar context, you get back the true/false (Number of matches,
actually) in $fee. You can get multiple returned values here:
if ( my ($fee, $fie, $foe, $fum ) = $foo =~
/(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/ ) {
printf('IP = "%d.%d.%d.%d"%s',
$fee, $fie, $foe, $fum, "\n") ;

using printf is a little more readable esp if the vars can sort line up
under their template markers. The "\n" on the end was one way to avoid \"
you could do
printf("IP = '%d.%d.%d.%d'%s",
$fee, $fie, $foe, $fum) ;

if:
IP = '10.20.30.40'

is acceptable.

Kevin wondered:
> but I thought the general purpose of this listserv was to
> discuss issues related to the ActiveState perl, not coding issue.

Maybe, but its been used as as such for so long, one'd have to go w/ a
"no, its for active perl users to ask perl questions". The unix-user and,
to a lesser extent, the win32-user perl lists have pretty much gone the
same route. I don't imagine there's enough 'just ActiveState' perl issues
to keep a list going ;-> that's a good thing.

a

Andy Bach
Systems Mangler
Internet: andy_bach@wiwb.uscourts.gov
VOICE: (608) 261-5738 FAX 264-5932

"CM/ECF is a complex unfinished suit. Pull on a loose cuff thread and
your pants fall down." MEC
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Re: Capturing parens regexp in one line?

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hi deane --

In a message dated 1/8/2007 3:11:24 P.M. Eastern Standard Time,
Deane.Rothenmaier@walgreens.com writes:

> Gurus,
>
> I've not seen this done, so I don't know if it can be, but...
> Is there a way to get $1 from a pair of parens in a regexp
> into a variable in one line? That is...
>
> my $foo = 'http://10.20.30.40/gargle';
>
> $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
> my $fee = $1;
>
> print "IP = \"$fee\"\n";
>
> ...is there some way to get the second and third lines into one line?
>
> Deane Rothenmaier


C:\@Work\Perl>perl -we "use strict; my $foo = 'http://10.20.30.40/gargle';
my ($ip) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/; print qq(IP =
'$ip' \n);
IP = '10.20.30.40'

C:\@Work\Perl>perl -we "use strict; my $foo = 'http://10.20.30.40/gargle';
my ($oct1, $oct2, $oct3, $oct4) = $foo =~ /(\d{1,3}) \. (\d{1,3}) \.
(\d{1,3}) \. (\d{1,3})/x;
print qq(IP = '$oct1 - $oct2 - $oct3 - $oct4' \n);
IP = '10 - 20 - 30 - 40'

hth -- bill walters



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RE: Recent posts

Hi Kevin,

I just looked at http://aspn.activestate.com/ASPN/Mail/About/ActivePerl/
and it says "Discussion of ActivePerl, ActiveState's binary distribution
of Perl". So, you're right.

We all occasionally need to be reminded of this fact. And, as you have
done, we need to be respectful, merciful, and instructive when someone
makes an occasional mistake.

-----Original Message-----
From: activeperl-bounces@listserv.ActiveState.com
[mailto:activeperl-bounces@listserv.ActiveState.com] On Behalf Of Kevin
Roland Viel
Sent: Monday, January 08, 2007 2:16 PM
To: activeperl@listserv.ActiveState.com
Subject: Recent posts

I could be wrong, and I certainly do not want to discourage anyone from
seeking help, but I thought the general purpose of this listserv was to
discuss issues related to the ActiveState perl, not coding issue.
beginners@perl.org might be a better place for questions concerning
coding
or use of perl. Beginners certainly has a higher volume and several
members usually respond to each post, and quickly at that.

Just a thought,

Kevin


Kevin Viel
PhD Candidate
Department of Epidemiology
Rollins School of Public Health
Emory University
Atlanta, GA 30322
_______________________________________________
ActivePerl mailing list
ActivePerl@listserv.ActiveState.com
To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs
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RE: Capturing parens regexp in one line?

From: activeperl-bounces@listserv.ActiveState.com
[mailto:activeperl-bounces@listserv.ActiveState.com] On Behalf Of
Octavian Rasnita
Sent: 08 January 2007 20:44
To: activeperl@listserv.ActiveState.com; Deane.Rothenmaier@walgreens.com
Subject: Re: Capturing parens regexp in one line?

> Hi,
>
> my $foo = 'http://10.20.30.40/gargle';
> my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g;
>
> Note the /g at the end.

Note that it is the list context (i.e. 'my ($fee) =') that causes the
pattern match to return the matching sub-expressions. The g modifier is
redundant in this case, as only a single match is required. See 'perldoc
perlop'.

HTH

--
Brian Raven

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RE: Capturing parens regexp in one line?

> > Hi,
>
> my $foo = 'http://10.20.30.40/gargle';
> my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g;
>
> Note the /g at the end.

> Note that it is the list context (i.e. 'my ($fee) =') that causes the
pattern match to return the matching sub-expressions. The g modifier is
redundant in this case, as only a single match is required.

Yeah, the /g though is pretty neat this way. If you've got more than one
IP say, on the line, you can use it like a little matching engine in a
while loop
my $foo = 'http://10.20.30.40/gargle
http://10.20.30.41/gargle
http://10.20.30.42/gargle';
my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g;

print "Got an ip: $fee\n";
while ( $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g ) {
my $fee = $1;
print "Got one ip: $fee\n";
} # while /g

gets:
Got an ip: 10.20.30.40
Got one ip: 10.20.30.40
Got one ip: 10.20.30.41
Got one ip: 10.20.30.42

However, you can't do:
while ( my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g ) {

as then the assignment to $fee is the main connective and the match
restarts each loop.

a

Andy Bach
Systems Mangler
Internet: andy_bach@wiwb.uscourts.gov
VOICE: (608) 261-5738 FAX 264-5932

"CM/ECF is a complex unfinished suit. Pull on a loose cuff thread and
your pants fall down." MEC
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Re: Capturing parens regexp in one line?

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In a message dated 1/9/2007 11:52:30 A.M. Eastern Standard Time,
Andy_Bach@wiwb.uscourts.gov writes:

> However, you can't do:
> while ( my ($fee) = $foo =~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g ) {
>
> as then the assignment to $fee is the main connective and the match
> restarts each loop.


however, if evaluated in ``true'' (?) list context rather than the boolean
context of
a while() { ... } loop, the //g is allowed to run to exhaustion. e.g.:

C:\@Work\Perl\wordplay>perl -we "use strict; my $octet = qr( \d{1,3} )x;
my $foo = 'http://10.2.3.4/gargle _http://1.200.3.5/gargle_
(http://1.200.3.5/gargle) _http://1.2.33.6/gargle'_ (http://1.2.33.6/gargle') ; print
qq(\n);
print qq(Got one ip: $_ \n) for $foo =~
/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g; print qq(\n);
map { print qq(got an ip: $_ \n) } $foo =~
/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g; print qq(\n);
for my $ip ($foo =~ /($octet \. $octet \. $octet \. $octet)/xg) { print
qq('nuther ip: $ip \n) }"

Got one ip: 10.2.3.4
Got one ip: 1.200.3.5
Got one ip: 1.2.33.6

got an ip: 10.2.3.4
got an ip: 1.200.3.5
got an ip: 1.2.33.6

'nuther ip: 10.2.3.4
'nuther ip: 1.200.3.5
'nuther ip: 1.2.33.6


br -- bill



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