Perl

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

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

Perl

use chilkat();

$success = 0;

$subject = "John Anders, +_+_+ Mary Robins $$$$";
$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";

# There are 2 matches:

# {
#   "named": {
#     "first": 1,
#     "last": 2
#   },
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "John Anders",
#           "idx": 0,
#           "len": 11
#         },
#         {
#           "cap": "John",
#           "idx": 0,
#           "len": 4
#         },
#         {
#           "cap": "Anders",
#           "idx": 5,
#           "len": 6
#         }
#       ]
#     },
#     {
#       "group": [
#         {
#           "cap": "Mary Robins",
#           "idx": 19,
#           "len": 11
#         },
#         {
#           "cap": "Mary",
#           "idx": 19,
#           "len": 4
#         },
#         {
#           "cap": "Robins",
#           "idx": 24,
#           "len": 6
#         }
#       ]
#     }
#   ]
# }

# To replace capture groups, write code to examine each capture group within
# each match, and provide a replacement string.
# Then call RegexReplace.

# For example, let's capitalize the first names, and add append "on" to the last name.
# After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

$firstNameIdx = $json->IntOf("named.first");
$lastNameIdx = $json->IntOf("named.last");

$sbTemp = chilkat::CkStringBuilder->new();

$i = 0;
$numMatches = $json->SizeOfArray("match");
while ($i < $numMatches) {

    $json->put_I($i);

    # The replacement string for the first name will be all uppercase.
    $json->put_J($firstNameIdx);
    $sbTemp->Clear();
    $json->StringOfSb("match[i].group[j].cap",$sbTemp);
    $sbTemp->ToUppercase();
    $json->UpdateSb("match[i].group[j].rep",$sbTemp);

    # Append "on" to the last name.
    $json->put_J($lastNameIdx);
    $sbTemp->Clear();
    $json->StringOfSb("match[i].group[j].cap",$sbTemp);
    $sbTemp->Append("on");
    $json->UpdateSb("match[i].group[j].rep",$sbTemp);

    $i = $i + 1;
}

# The JSON now has replacement strings:
print $json->emit() . "\r\n";

# {
#   "named": {
#     "first": 1,
#     "last": 2
#   },
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "John Anders",
#           "idx": 0,
#           "len": 11
#         },
#         {
#           "cap": "John",
#           "idx": 0,
#           "len": 4,
#           "rep": "JOHN"
#         },
#         {
#           "cap": "Anders",
#           "idx": 5,
#           "len": 6,
#           "rep": "Anderson"
#         }
#       ]
#     },
#     {
#       "group": [
#         {
#           "cap": "Mary Robins",
#           "idx": 19,
#           "len": 11
#         },
#         {
#           "cap": "Mary",
#           "idx": 19,
#           "len": 4,
#           "rep": "MARY"
#         },
#         {
#           "cap": "Robins",
#           "idx": 24,
#           "len": 6,
#           "rep": "Robinson"
#         }
#       ]
#     }
#   ]
# }

# Call RegexReplace to update the StringBuilder with the replacements.
$success = $sb->RegexReplace($json);
if ($success == 0) {
    print $sb->lastErrorText() . "\r\n";
    exit;
}

print "Result after doing replacements:" . "\r\n";
print $sb->getAsString() . "\r\n";

# Result after doing replacements:
# JOHN Anderson, +_+_+ MARY Robinson $$$$