Check content of file and add string if not exists - string

Question

I want to do the following:
I need to check the content of a (text) file. If a defined string is not there, it has to be inserted on a specific position.
I.e.:
My textfile is a configuration file with different sections, example:
[default]
name=bob
alias=alice
foo=bar
example=value
[conf]
name=value
etc=pp
I want to check if the string “foo=bar” and “example=value” exists in this file. If not, it has to get inserted, but I can't just append the new lines, since they have to be in the certain (here [default]) section and not to the end of the file. The position within the section doesn’t matter.
I tried with the following PowerShell script, which actually just looks for a definitely existing string and adds the new lines after it. Therefore I can make sure that the new lines get inserted in the right section, but I can't make sure that they won't be doubled, since my script doesn't check if they already exist.
$InputFile = "C:\Program Files (x86)\Path\to\file.ini"
$find = [regex]::Escape("alias=alice")
$addcontent1 = "foo=bar"
$addcontent2 = " example=value `n"
$InputFileData = Get-Content $InputFile
$matchedLineNumber = $InputFileData |
Where-Object{$_ -match $find} |
Select-Object -Expand ReadCount
$InputFileData | ForEach-Object{
$_
if ($_.ReadCount -eq ($matchedLineNumber)) {
$addcontent1
$addcontent2
}
} | Set-Content $InputFile

Answer 1

As mentioned by Bill_Stewart, Ansgar Wiechers and LotPings there are multiple modules to work with .ini files available in the web.
Let's take this one for example. Once you download it and import you can see how it imports your file (I removed foo=bar to demonstrate):
PS C:\SO\51291727> $content = Get-IniContent .\file.ini
PS C:\SO\51291727> $content
Name Value
---- -----
default {name, alias, example}
conf {name, etc}
From here what you want to do is pretty simple - check if key exists and if not - add:
if ($content.default.foo -ne 'bar') {
$content.default.foo='bar'
}
Verify that the value has been inserted:
PS C:\SO\51291727> $content.default
Name Value
---- -----
name bob
alias alice
example value
foo bar
And export:
$content | Out-IniFile .\out.ini