perl regex question

[Chad Williams]

my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9
fpu_type sparcv9 clock_MHz 450";

How come this:

$procspeed=~ s/.*\s(\d+)\w*/$1/;

gives me $procspeed=450

but this:

$procspeed=~ s/.*\s(\d+)\w*$/$1/;

matches the whole line?

What's the most efficient way to do this? (get the last word/word of
digits, etc)

TIA

[Matija Papec]

X-Ftn-To: Chad Williams

[email]chad_dude@yahoo.com[/email] (Chad Williams) wrote:

>my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9
>fpu_type sparcv9 clock_MHz 450";
>
>How come this:
>
>$procspeed=~ s/.*\s(\d+)\w*/$1/;
>
>gives me $procspeed=450
>
>but this:
>
>$procspeed=~ s/.*\s(\d+)\w*$/$1/;
>
>matches the whole line?
>
>What's the most efficient way to do this? (get the last word/word of
>digits, etc)

Don't know for most efficient but this is the simplest :)
print ($procspeed =~ /(\d+)/g)[-1]



--
Matija

[John Bokma]

Matija Papec wrote:

> X-Ftn-To: Chad Williams
>
> [email]chad_dude@yahoo.com[/email] (Chad Williams) wrote:
>

>>my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9
>>fpu_type sparcv9 clock_MHz 450";
>>
>>How come this:
>>
>>$procspeed=~ s/.*\s(\d+)\w*/$1/;
>>
>>gives me $procspeed=450
>>
>>but this:
>>
>>$procspeed=~ s/.*\s(\d+)\w*$/$1/;
>>
>>matches the whole line?
>>
>>What's the most efficient way to do this? (get the last word/word of
>>digits, etc)

>
>
> Don't know for most efficient but this is the simplest :)
> print ($procspeed =~ /(\d+)/g)[-1]

print substr($procspeed, -3);

assuming it is always between 100 and 999.

--
Kind regards, feel free to mail: mail(at)johnbokma.com (or reply)
virtual home: [url]http://johnbokma.com/[/url] ICQ: 218175426
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[John W. Krahn]

Chad Williams wrote:

>
> my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9
> fpu_type sparcv9 clock_MHz 450";
>
> How come this:
>
> $procspeed=~ s/.*\s(\d+)\w*/$1/;
>
> gives me $procspeed=450
>
> but this:
>
> $procspeed=~ s/.*\s(\d+)\w*$/$1/;
>
> matches the whole line?

They both match the same thing. The $ anchor doesn't make a difference
because the .* at the beginning is greedy.


John
--
use Perl;
program
fulfillment

[Glenn Jackman]

Chad Williams <chad_dude@yahoo.com> wrote:

> my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9 fpu_type sparcv9 clock_MHz 450";

[...]

> What's the most efficient way to do this? (get the last word/word of
> digits, etc)

Also,
my ($last_digits) = $procspeed =~ m{
(\d+) # a sequence of digits
\D*$ # followed by non-digits at the end of the string
}x;

--
Glenn Jackman
NCF Sysadmin
[email]glennj@ncf.ca[/email]

[Jeff 'japhy' Pinyan]

[posted & mailed]

On 10 Sep 2003, Chad Williams wrote:

>my $procspeed="state on-line state_begin 1058768026 cpu_type sparcv9
>fpu_type sparcv9 clock_MHz 450";
>
>How come this:
>
>$procspeed=~ s/.*\s(\d+)\w*/$1/;
>
>gives me $procspeed=450
>
>but this:
>
>$procspeed=~ s/.*\s(\d+)\w*$/$1/;
>
>matches the whole line?

They should both result in $procspeed being 450. (They do for me.)

>What's the most efficient way to do this? (get the last word/word of
>digits, etc)

You can use the .* approach, but you need to be sure you write it
properly. You did, ensuring there's a space before the digits. If you
had left it out, $procspeed would only be '0', since the .* is greedy, and
(\d+) is content in just matching one digit.

I wouldn't suggest the /(\d+)\D*$/ approach, because it requires you try
to match at EACH chunk of digits. If there are many chunks of digits in
your string, that'll be inefficient.

I personally suggest reversing the string, matching the "first" set of
digits, and then reversing that match.

$last_num = reverse( (reverse($str) =~ /(\d+)/)[0] );

Or:

$last_num = reverse $1 if reverse($str) =~ /(\d+)/;

--
Jeff Pinyan RPI Acacia Brother #734 2003 Rush Chairman
"And I vos head of Gestapo for ten | Michael Palin (as Heinrich Bimmler)
years. Ah! Five years! Nein! No! | in: The North Minehead Bye-Election
Oh. Was NOT head of Gestapo AT ALL!" | (Monty Python's Flying Circus)

[Quantum Mechanic]

[email]chad_dude@yahoo.com[/email] (Chad Williams) wrote:

> What's the most efficient way to do this? (get the last word/word of
> digits, etc)

Generally slower to faster options:

$last_word = ($string =~ /(\w+)/g)[-1]; # only keep the last word

$last_word = reverse ( (reverse $string) =~ /(\w+)/ ); # double reverse

$last_word = (split /\W+/, $string )[-1];

$last_word = reverse( (split /\W+/, reverse $string, 2 )[0] );

-QM

[Matija Papec]

On Wed, 10 Sep 2003 17:56:46 -0400, Jeff 'japhy' Pinyan
<pinyaj@rpi.edu> wrote:

>I wouldn't suggest the /(\d+)\D*$/ approach, because it requires you try
>to match at EACH chunk of digits. If there are many chunks of digits in
>your string, that'll be inefficient.
>
>I personally suggest reversing the string, matching the "first" set of
>digits, and then reversing that match.
>
> $last_num = reverse( (reverse($str) =~ /(\d+)/)[0] );

I guess index can be left out since list has only one value,
$last_num = reverse( reverse($procspeed) =~ /(\d+)/ );