Replacing a substring inside a string in powershell script - string

Question

I have long text files, containing markup for another software. The form of the text is this:
*INIT=D:\ws\**randomnonesense*
ROW=THISISROW,D:\ws\morestuff
PALVELU=200,WSTIME70.DLL,N,A
PALVELU=201,WSLDIR70.DLL,N,A
PALVELU=202,WSLDIX70.DLL,N,A
PALVELU=204,WSEXCE32.DLL,N,A
PALVELU=205,WMON.DLL,N,A
PALVELU=206,WSWORD32.DLL,N,A
PALVELU=207,WSLEPT32.DLL,N,A
PALVELU=208,WSCONV70.DLL,N,A
PALVELU=209,WSFTPC70.DLL,N,A
KUVAUS=\\192.168.169.17\adwise$\applic\LIKSA_TURE.A70,D:\ws\%aspno%\%username%
MDBS-KANTA=LIKSAV,%aspno%LIK.DB,5,RTTL,ANSI,111.111.111.11MDBS-
KANTA=LANKA,%aspno%LAN.DB,5,RTTL,ANSI,1000.000.111.11
I am writing a script, that needs to replace all of those rows that start with the word PALVELU. The amount of other stuff before and after those rows can be any. Also number of those PALVELU-rows or their lenght is not the same in every file. Still I would need to replace all of those rows in every file with another set of rows. Is there a way to do this?

Answer 1

You can use the following method:
Replace(oldStr, newStr)
eg:
Write-Host "replacing a text in string"
$test=" old text to be replaced"
Write-Host "going to replace old"
$test.Replace("old","New")
Write-Host "Text is replaced"
Hope this will helpful.

Answer 2

You can use [regex]::split to split content of your file by lines, after you have all line you can check if each line contain the word PALVELU using -like operator.
I use \n in the regex pattern to split your content on every start of a newline
$rows = [regex]::split("*INIT=D:\ws\**randomnonesense*
ROW=THISISROW,D:\ws\morestuff
PALVELU=200,WSTIME70.DLL,N,A
PALVELU=201,WSLDIR70.DLL,N,A
PALVELU=202,WSLDIX70.DLL,N,A
PALVELU=204,WSEXCE32.DLL,N,A
PALVELU=205,WMON.DLL,N,A
PALVELU=206,WSWORD32.DLL,N,A
PALVELU=207,WSLEPT32.DLL,N,A
PALVELU=208,WSCONV70.DLL,N,A
PALVELU=209,WSFTPC70.DLL,N,A
KUVAUS=\\192.168.169.17\adwise$\applic\LIKSA_TURE.A70,D:\ws\%aspno%\%username%
MDBS-KANTA=LIKSAV,%aspno%LIK.DB,5,RTTL,ANSI,111.111.111.11MDBS-
KANTA=LANKA,%aspno%LAN.DB,5,RTTL,ANSI,1000.000.111.11", "(.*)\n")
$output = [System.Collections.ArrayList]#()
foreach($row in $rows) {
if($row -like '*PALVELU*') {
$output.Add($row.Replace("PALVELU", "TEST")) | Out-Null
} else {
$output.Add($row) | Out-Null
}
}

Answer 3

If the goal is to replace each PALVELU row with a new row, you may do the following:
# Assumes your file is a.txt
$ReplaceThis = '^PALVELU.*$'
$ReplaceWith = '<new row>'
$(switch -regex -file a.txt {
$ReplaceThis { $_ -replace $ReplaceThis,$ReplaceWith }
Default { $_ }
}) | Set-Content a.txt
The code above will result in X number of PALVELU rows being replaced with X number of <new row>.
If the goal is to replace consecutive PALVELU rows with a single <new row> string in files that only contain one set of consecutive PALVELU rows, you may do the following:
$ReplaceThis = '(?sm)^PALVELU.*(?-s)^PALVELU.*$'
$ReplaceWith = '<new row>'
(Get-Content a.txt -Raw) -replace $ReplaceThis,$ReplaceWith |
Set-Content a.txt
If the goal is to replace all PALVELU rows with a single <new row> string at the location of the first PALVELU row and the rows could be anywhere in the file, you may do the following:
$ReplaceThis = '^PALVELU.*$'
$ReplaceWith = '<new row>'
$firstMatch = $false
$(switch -regex -file a.txt {
$ReplaceThis {
if ($firstMatch) {
$_ -replace $ReplaceThis
}
else {
$_ -replace $ReplaceThis,$ReplaceWith
$firstMatch = $true
}
}
default { $_ }
}) -ne '' | Set-Content a.txt