How can i modify part of a row in file?

Question

I have a file witch contains multiple rows with strings like this:

DTSTART:20190716T180000

DTEND:20190716T180000

I want to modify every DTEND row. I want to replace the 180000 with 190000. The Parts between DTEND: and 180000 are different each time. Does anyone now how I can change the string in powershell?

Answer 1

here's one way to do the job. [grin] it finds a line that starts with DTEND, grabs the timestamp, converts it to a [datetime] object, adds one hour to it, reformats that to the same layout as the original, builds a new line, and then outputs it to the $Results collection.

the collection can be sent to a file or screen as desired.

# fake reading in a text file
#    in real life, use Get-Content
$InStuff = @'
DTSTART:20190716T180000
DTEND:20190716T180000
'@ -split [System.Environment]::NewLine

$Marker = 'DTEND'
$HoursToAdd = 1

$Results = foreach ($IS_Item in $InStuff)
    {
    if ($IS_Item -match "^$Marker")
        {
        $Prefix, $OldTimeStamp = $IS_Item.Split(':')
        $NewTimeStamp = [datetime]::ParseExact($OldTimeStamp, 'yyyyMMddTHHmmssss', $Null).
            AddHours($HoursToAdd).
            ToString('yyyyMMddTHHmmssss')

        ($Prefix, $NewTimeStamp) -join ':'
        }
        else
        {
        $IS_Item
        }
    }

$Results

output ...

DTSTART:20190716T180000
DTEND:20190716T190000