reversing substr

[DaWolf]

Greetings, fellow monks.

I have a question that's probably not original but I was unable to find it on supersearch.

I know that if you put the following code:

my $str = "1234";
my $ss = substr ($str,2);
print $ss;

will return 34

Well, I need the opposite, meaning a substr that cuts the string from the right, not from the left...

I've tried entering a negative offset - sounds logic to me - but that doesn't work...

So, what's the trick?

Thanks in advance,

Er Galvão Abbott
a.k.a. Lobo, DaWolf
Webdeveloper

[abstracts]

Hello,

What you want to do probably falls into one of these cases:

# dashes are just for illustration
my $str =                  "123456789";
my $ss = substr ($str,3);
print "$ss\n"; # will print ---456789
$ss = substr ($str,-3);
print "$ss\n"; # will print ------789
$ss = substr ($str,0,3);
print "$ss\n"; # will print 123------
$ss = substr ($str,0,-3);
print "$ss\n"; # will print 123456---

Check out perlfunc substr to know more about it since this function in particular has a very informative description with lots of examples.

Hope this helps,,,
Aziz,,,

[chipmunk]

It's not quite clear what you're trying to do, especially since substr does accept a negative offset. What do you mean when you say "that doesn't work"?

If you want the first two characters of the string, try this:

my $str = "12345";
my $ss = substr($str, 0, 2);
print $ss;

Or, if you want all but the last two characters, try this:

my $str = "12345";
my $ss = substr($str, 0, -2);
print $ss;

[talexb]

Check out perlfunc:substr for information on how substr works -- you can find it on this site by typing in 'substr' in the search field at the top left of your screen.

--t. alex

"There was supposed to be an earth-shattering kaboom!" --Marvin the Martian

[davis]

Hi there,
I'm a little unsure as to what you're asking, but if you're asking for the substring you create to be reversed, you can use reverse thusly:

my $str = "1234";
my $ss  = reverse substr($str, 2);
print $ss;

Hope that helps,
davis
Is this going out live?
No, Homer, very few cartoons are broadcast live - it's a terrible strain on the animator's wrist

[jlongino]

If you're looking for something truncate the string, then you might want to look into the pack function. It has the added advantage of right-padding the string with blanks:

use strict;
my $str = "1234";

my $ss = pack "A2", $str;
print "'$ss'\n";

### example shows example of padding blanks
$ss = pack "A5", $str;
print "'$ss'\n";

Produces:

'12'
'1234 '

--Jim