PowerShell Extract Number Between Square Brackets And Insert Into Following Line

Question

I am trying to insert the item number extracted from preceding line. I have a file with groups of text that are numbered in square brackets.

For example

some text

line 1: [1]
line 2: id = Item 

line 1: [2]
line 2: id = Item 

Should be changed to:

some text

line 1: [1]
line 2: id = Item 1

line1: [2]
line 2: id = Item 2

$filepath = "D:\Users\j\Desktop\New folder\Environment-p.ini"
get-content $filepath | $itemnumber = select-string '(?<=\[)[^]]+(?=\])').matches.value | $iteminsertnumber = select-string -pattern "Item" | $iteminsertnumber.replace("Item","Item $itemnumber") | out-file "D:\Users\j\Desktop\New folder\Environment-p mod.ini"

$filepath = "D:\Users\j\Desktop\New folder\Environment-p.ini"
get-content $filepath | select-string -pattern "(?=\[).*?(?=\])" -context 0, 1 | foreach {$_.matches.value} | -replace $_.context.postcontext('Item',"Item $_") | set-content "D:\Users\j\Desktop\New folder\Environment-p mod.ini"

Answer 1

A switch with the -Regex flag could work for this, as an example:

$content = @'
some text

line 1: [1]
line 2: id = Item

line 1: [2]
line 2: id = Item

line 1: [123]
line 2: id = Item
'@ -split '\r?\n'

switch -Regex ($content) {
    '(?<=\[)[^\]]+' {
        # capture whats between brackets
        $value = $Matches[0]
        # output the line
        $_
        # go to next line
        continue
    }
    # if there was a capture previously
    { $value } {
        # replace the end of the line including
        # any possible whitespaces before it
        # with a space and the captured value
        $_ -replace '\s*$', " $value"
        # reset the value
        $value = $null
        # go to next line
        continue
    }
    # output this line if none of the above
    Default { $_ }
}

If you're reading a file you would use the -File parameter, logic is still the same:

# this outer scriptblock allows us to pipe the output
# from the switch to Set-Content
& {
    switch -Regex -File $filepath {
        # same logic here
    }
} | Set-Content path\to\resultfile.ext