PowerShell Requires Chilkat v11.1.0+

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

PowerShell

Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

$subject = "John Anders, +_+_+ Mary Robins $$$$"
$pattern = "(?<first>\\w+)\\s+(?<last>\\w+)"

$sb = New-Object Chilkat.StringBuilder
$sb.Append($subject)

$json = New-Object Chilkat.JsonObject
$json.EmitCompact = $false

$timeoutMs = 2000
$numMatches = $sb.RegexMatch($pattern,$json,$timeoutMs)
if ($numMatches -lt 0) {
    #  Probably an error in the regular expression.
    #  Suggestion: Use AI to help create and/or diagnose regular expressions.
    $($sb.LastErrorText)
    exit
}

#  Examine the matches:
$($json.Emit())

#  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 = New-Object Chilkat.StringBuilder

$i = 0
$numMatches = $json.SizeOfArray("match")
while ($i -lt $numMatches) {

    $json.I = $i

    #  The replacement string for the first name will be all uppercase.
    $json.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.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:
$($json.Emit())

#  {
#    "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 -eq $false) {
    $($sb.LastErrorText)
    exit
}

$("Result after doing replacements:")
$($sb.GetAsString())

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