Tcl Requires Chilkat v11.1.0+

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

Tcl

load ./chilkat.dll

set success 0

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

set sb [new_CkStringBuilder]

CkStringBuilder_Append $sb $subject

set json [new_CkJsonObject]

CkJsonObject_put_EmitCompact $json 0

set timeoutMs 2000
set numMatches [CkStringBuilder_RegexMatch $sb $pattern $json $timeoutMs]
if {$numMatches < 0} then {
    #  Probably an error in the regular expression.
    #  Suggestion: Use AI to help create and/or diagnose regular expressions.
    puts [CkStringBuilder_lastErrorText $sb]
    delete_CkStringBuilder $sb
    delete_CkJsonObject $json
    exit
}

#  Examine the matches:
puts [CkJsonObject_emit $json]

#  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:

CkJsonObject_put_I $json [CkJsonObject_IntOf $json "named.first"]
puts "first: [CkJsonObject_stringOf $json {match[0].group[i].cap}]"

CkJsonObject_put_I $json [CkJsonObject_IntOf $json "named.last"]
puts "last: [CkJsonObject_stringOf $json {match[0].group[i].cap}]"

#  Output is: 

#  first: John
#  last: Smith

delete_CkStringBuilder $sb
delete_CkJsonObject $json