Perl

Regular Expression with Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups.

See the sample code below.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

In PCRE2, named capture groups allow you to assign a name to a capturing group, making it easier to reference by name instead of number.

Syntax

(?<name>pattern)

or

(?'name'pattern)

Example

(?<first>\w+)\s+(?<last>\w+)

Applied to:

"John Smith"

Produces:

• first: John
• last: Smith

Perl

use chilkat();

$success = 0;

$subject = "John Smith";
$pattern = "(?<first>\\w+)\\s+(?<last>\\w+)";

$sb = chilkat::CkStringBuilder->new();
$sb->Append($subject);

$json = chilkat::CkJsonObject->new();
$json->put_EmitCompact(0);

$timeoutMs = 2000;
$numMatches = $sb->RegexMatch($pattern,$json,$timeoutMs);
if ($numMatches < 0) {
    # Probably an error in the regular expression.
    # Suggestion: Use AI to help create and/or diagnose regular expressions.
    print $sb->lastErrorText() . "\r\n";
    exit;
}

# Examine the matches:
print $json->emit() . "\r\n";

# Here is the JSON showing the matches.
# Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

# {
#   "named": {
#     "first": 1,
#     "last": 2
#   },
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "John Smith",
#           "idx": 0,
#           "len": 10
#         },
#         {
#           "cap": "John",
#           "idx": 0,
#           "len": 4
#         },
#         {
#           "cap": "Smith",
#           "idx": 5,
#           "len": 5
#         }
#       ]
#     }
#   ]
# }

# The capture group index is obtained by looking up the name in the JSON result.
# For example:

$json->put_I($json->IntOf("named.first"));
print "first: " . $json->stringOf("match[0].group[i].cap") . "\r\n";

$json->put_I($json->IntOf("named.last"));
print "last: " . $json->stringOf("match[0].group[i].cap") . "\r\n";

# Output is: 

# first: John
# last: Smith