CODEWITHSUNDEEP
regexperl
bana
bana

Reputation: 397

Perl regex is not giving the expected result

I have following code 

  my $string = 'ban-3.1.2278-1.x86_64.1.rpm';
  my ($substr) = ($string =~ /(.+)-\d(.+)/);
  print "Result: $substr\n";

I was expecting it to return ban but its returning ban-3.1.2278, I am not able to figure it out why. Can anyone please explain me why its behaving it this way and whats the correct way to do it ?

thank you.

Upvotes: 0

Views: 77

Answers (4)

mkHun
mkHun

Reputation: 5927

Split also gives what you expect. try this

my $string = 'ban-3.1.2278-1.x86_64.1.rpm';
my @substr = split('-',$string);
print "Result: $substr[0]\n";

Output

Result: ban

This script is split by the - the which is store into the array. Then print the ban by using index key value like $substr[0]

Upvotes: 1

Sabari
Sabari

Reputation: 1

In the above code "my ($substr) = ($string =~ /(.+?)-\d(.+)/);", unnecessary grouping are used. Use the following code instead of that,

my $string = 'ban-3.1.2278-1.x86_64.1.rpm'; 
$string =~ /([a-z]+)-/i; 
print "Result: $1";

If you need an answer only "ban" means use this code.

[a-z]+ - it matches more than one continuous alphabet characters(accurate matches).

i - it used for case sensitive.

$1 - it returns the value of first grouping.

OUTPUT

Result: ban

Upvotes: 0

Avinash Raj
Avinash Raj

Reputation: 174696

You need to make .+ inside the first capturing group as non-greedy by adding a quantifier ? after + so that it would do a reluctant match(ie, shortest possible match) or otherwise it would do a longest match. 

(.+?)-\d(.+)

Code:

my $string = 'ban-3.1.2278-1.x86_64.1.rpm';
my ($substr) = ($string =~ /(.+?)-\d(.+)/);
print "Result: $substr\n";

Output:

Result: ban

Upvotes: 1

Miller
Miller

Reputation: 35198

Because the any character . will match dashes.

If you want to limit he matching, use a characters class or non-greedy matching .*?:

my $string = 'ban-3.1.2278-1.x86_64.1.rpm';
my ($substr) = $string =~ /([^-]*)-\d(.+)/;
print "Result: $substr\n";

Outputs:

Result: ban

Upvotes: 2

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