Substring doubt?

[lilly07]

Hi

Please let me know any fnction to do this. I have started learning perl and any guidance would be useful.

Suppose I have a string as below;

my $string = 'Nowisthetimeforallgoodpeopletocometotheaidoftheirparty';

Suppose if I want to look for a word

time

, I can use a regex to find whether he string contains the word time or not.

But I need a way to chop the original string and count the number of characters in that string.

In tha above example

Nowisthe

is the one I am interested. string before time is

Nowisthe

and the length of the string is 8. How do I do it programatically? Thanks.

[nithinpes]

If you are trying to capture the string preceeding the match, you can make use of the special variable $`. e.g

my $string = 'Nowisthetimeforallgoodpeopletimetocometotheaidoftheir  party'; 
 
if($string=~/time/) {
my $pre = $`; # get characters preceeding the match
my $length=length($pre);
print "$pre  : ($length)\n"
}
 

This will produce:

Nowisthe  : (8)
 

Similarly, $' can be used to capture string succeeding the match.

[KevinADC]

If you are really wanting to find where a substring is in a string as versus finding a pattern, the index function is made for that:

my $string = 'Nowisthetimeforallgoodpeopletocometotheaidoftheirparty';
my $where = index $string, 'time';
print $where;

The suggestion nithinpes has posted is an easy one to implement as it takes advantage of some of perls builtin variables and is easy to stick into a script and getting working. It unfortunately inccurs a considerable performance penalty on any other regexps used in the code. An alternative is to use another perl builtin that does not introduce the performance penalty: @-

my $string = 'Nowisthetimeforallgoodpeopletimetocometotheaidoftheirparty'; 
if($string=~/time/) {
   print $-[0]; # get the offset
}

[nithinpes]

The suggestion nithinpes has posted is an easy one to implement as it takes advantage of some of perls builtin variables and is easy to stick into a script and getting working. It unfortunately inccurs a considerable performance penalty on any other regexps used in the code. An alternative is to use another perl builtin that does not introduce the performance penalty: @-

my $string = 'Nowisthetimeforallgoodpeopletimetocometotheaidoftheirparty'; 
if($string=~/time/) {
   print $-[0]; # get the offset
}

That's cool :) . I never knew of @-.

[KevinADC]

Theres also @+. You can read about them in perlvar