PowerShell

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 $$$$