Function to replace text in a file and save it - powershell

Question

I am new programming, I am trying to improve the following code of a script, I was thinking of making a function to improve it but I do not know where to start or if it is the best option.
$replaceText01 = (Get-Content -path $copyFileLocation -Raw) -replace '"INSTANCENAME="TEST""',$NUEVAINESTANCIA
Set-Content $copyFileLocation $replaceText01
$replaceText02 = (Get-Content -path $copyFileLocation -Raw) -replace '"INSTANCEID="TEST""',$NUEVAINESTANCIAID
Set-Content $copyFileLocation $replaceText02
$replaceText03 = (Get-Content -path $copyFileLocation -Raw) -replace "NT Service\SQLAgent#TEST", $CUENTAAGTN
Set-Content $copyFileLocation $replaceText03
$replaceText04 = (Get-Content -path $copyFileLocation -Raw) -replace "NT Service\MSSQL#TEST", $CUENTASQLSER
Set-Content $copyFileLocation $replaceText04
$user = "$env:UserDomain\$env:USERNAME"
write-host $user
$replaceText = (Get-Content -path $copyFileLocation -Raw) -replace "##MyUser##", $user
Set-Content $copyFileLocation $replaceText

Answer 1

First off, I would probably try to read the file only once. Then since you are doing many similar operations, I would put all the data about the operations in an array, and then iterate over those data.
In this code, I first read the file. Then I define all the strings that should be replaced together with the strings that should replace them. Then I use a loop to iterate over the data so that we don't repeat the same code all the time.
$data = Get-Content -Path $copyFileLocation -Raw
$replacements = #(
#('"INSTANCENAME="TEST""', $NUEVAINESTANCIA),
#('"INSTANCEID="TEST""', $NUEVAINESTANCIAID),
#("NT Service\SQLAgent#TEST", $CUENTAAGTN),
#("NT Service\MSSQL#TEST", $CUENTASQLSER),
#("##MyUser##", "$env:UserDomain\$env:USERNAME")
)
$replacements | ForEach-Object {
$data = $data.Replace($_[0], $_[1])
}
Set-Content -Path $copyFileLocation -Value $data
It's also possible to get this even shorter if you use the pipeline instead of assigning the data to a variable
$data = Get-Content -Path $copyFileLocation -Raw
#(
#('"INSTANCENAME="TEST""', $NUEVAINESTANCIA),
#('"INSTANCEID="TEST""', $NUEVAINESTANCIAID),
#("NT Service\SQLAgent#TEST", $CUENTAAGTN),
#("NT Service\MSSQL#TEST", $CUENTASQLSER),
#("##MyUser##", "$env:UserDomain\$env:USERNAME")
) | ForEach-Object {
$data = $data.Replace($_[0], $_[1])
}
Set-Content -Path $copyFileLocation -Value $data
Edit: Missed that you were asking on how to make it into a function.
By looking at what your doing I assume you are modifying an SQL unattended install file, and have named it as such.
A good idea here is to make most of the parameters mandatory, so you are sure the user at least specifies all the required parameters. Maybe you want to specify MyUser later, so this is a good candidate for being a parameter with a default value.
Function Set-SQLInstallFileVariables {
Param(
[Parameter(Mandatory)][string]$FilePath,
[Parameter(Mandatory)][string]$NUEVAINESTANCIA,
[Parameter(Mandatory)][string]$NUEVAINESTANCIAID,
[Parameter(Mandatory)][string]$CUENTAAGTN,
[Parameter(Mandatory)][string]$CUENTASQLSER,
[string]$MyUser = "$env:UserDomain\$env:USERNAME"
)
$data = Get-Content -Path $FilePath -Raw
#(
#('"INSTANCENAME="TEST""', $NUEVAINESTANCIA),
#('"INSTANCEID="TEST""', $NUEVAINESTANCIAID),
#("NT Service\SQLAgent#TEST", $CUENTAAGTN),
#("NT Service\MSSQL#TEST", $CUENTASQLSER),
#("##MyUser##", $MyUser)
) | ForEach-Object {
$data = $data.Replace($_[0], $_[1])
}
Set-Content -Path $copyFileLocation -Value $data
}

Answer 2

The first thing to notice is that you read and write the file over and over again on every replacement, which is not very efficient.
This is not needed; once read the content is in a string variable and can get manipulated in memory multiple times before writing back to file.
One approach is to use string arrays that hold the search and replacement strings.
For this to work properly, both arrays must have the same number of elements.
$inputFile = 'D:\Test\TheFile.txt' # your input file path here ($copyFileLocation)
$outputFile = 'D:\Test\TheReplacedFile.txt' # for safety create a new file instead of overwriting the original
$searchStrings = '"INSTANCENAME="TEST""','"INSTANCEID="TEST""',"NT Service\SQLAgent#TEST","NT Service\MSSQL#TEST","##MyUser##"
$replaceStrings = $NUEVAINESTANCIA, $NUEVAINESTANCIAID, $CUENTAAGTN, $CUENTASQLSER, "$env:UserDomain\$env:USERNAME"
# get the current content of the file
$content = Get-Content -path $copyFileLocation -Raw
# loop over the search and replace strings to do all replacements
for ($i = 0; $i -lt $searchStrings.Count; $i++) {
$content = $content -replace [regex]::Escape($searchStrings[$i]), $replaceString[$i]
}
# finally, write the updated content to a (new) file
$content | Set-Content -Path $copyFileLocation
Another approach would be to use a Hashtable that stores both the search strings and the replacement strings:
$inputFile = 'D:\Test\TheFile.txt' # your input file path here ($copyFileLocation)
$outputFile = 'D:\Test\TheReplacedFile.txt' # for safety create a new file instead of overwriting the original
$hash = #{
'"INSTANCENAME="TEST""' = $NUEVAINESTANCIA
'"INSTANCEID="TEST""' = $NUEVAINESTANCIAID
"NT Service\SQLAgent#TEST" = $CUENTAAGTN
"NT Service\MSSQL#TEST" = $CUENTASQLSER
"##MyUser##" = "$env:UserDomain\$env:USERNAME"
}
# get the current content of the file
$content = Get-Content -path $copyFileLocation -Raw
# loop over the items in the hashtable to do all replacements
$hash.GetEnumerator() | ForEach-Object {
# the `$_` is an automatic variable you get within a ForEach-Object{}
# It represents a single item on each iteration.
$content = $content -replace [regex]::Escape($_.Key), $_.Value
}
# finally, write the updated content to a (new) file
$content | Set-Content -Path $copyFileLocation
In both cases, we're using -replace, which is a case-insensitive regex replacement. Because your search strings hold characters that have special meaning in regex (# and \) we need to escape these with [regex]::Escape()
Hope that helps

Answer 3

Here is mine attempt at it. Its not meant to be lean. Rather to be really clear about what it is doing while being full of functions (too many) and stopping you from getting the content multiple times.
After seeing what everyone else answered, their's is better code. Hopefully mine is readable and give you a better idea about using the pipeline and functions :)
Function Replace1 {Process{$_ -replace '"INSTANCENAME="TEST""',$NUEVAINESTANCIA}}
Function Replace2 {Process{$_ -replace '"INSTANCEID="TEST""',$NUEVAINESTANCIAID}}
Function Replace3 {Process{$_ -replace "NT Service\SQLAgent#TEST", $CUENTAAGTN}}
Function Replace4 {Process{$_ -replace "NT Service\MSSQL#TEST", $CUENTASQLSER}}
Function Replace6 {Process{$_ -replace "##MyUser##", $user}}
$user = "$env:UserDomain\$env:USERNAME"
Write-Host $user
Get-Content -path $copyFileLocation | Replace1 | Replace2 | Replace3 | Replace4 | Replace5 | Replace6 | Set-Content -path $copyFileLocation