Powershell find a string after specific line

Question

I have a log file that appends a "restart successfully" line after each restart. Starting from the last "restart successfully" line, I want to find any lines after that contain a word from a list of search words.

How can I do this? I have partly working code below:

$contentsOfLog = Get-Content $inputFile
$keyWords =  $contentsOfLog | Select-String 'restart successfully'
$linenumbers = $keyWords.LineNumber
$linenumber = $linenumbers[$linenumbers.Length - 1]

$inputLines = ""

For ($i=$linenumber; $i -lt $contentsOfLog.length; $i++) {
    $line = $contentsOfLog[$i]
    $line = $line|select-string -pattern $error|Out-String
    $inputLines += $line.TrimEnd()
}

Mathias R. Jessen · Accepted Answer · 2020-05-20 14:07:36Z

2

Obtain the line number to start from with a first pass through Select-String like you've already found, then use Select-Object -Skip to skip the lines prior:

$contentsOfLog = Get-Content $inputFile
$startFrom = $contentsOfLog |Select-String 'restart successfully' |Select -Last 1 -Expand LineNumber

$inputLines = $contentsOfLog |Select -Skip $startFrom |Select-String $error |Select -Expand Line

answered May 20, 2020 at 14:07

Mathias R. Jessen

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1 Comment

Bugs Bunny Over a year ago

Thanks a lot Mathias as always :)

garethTheRed · Accepted Answer · 2023-09-01 07:03:43Z

0

If you have a limit on the expected number of lines after your search string, then you can use Select-String's -Context switch:

$contentsOfLog = Get-Content $inputFile
($contentsOfLog | Select-String 'restart successfully' -Context 0,999).Context.PostContext | Select-String $error

This has the advantage that you're parsing in one pass, but the disadvantage that you need to have a limit on the number of lines searched. Note that setting the second number (999 in my example) to a ridiculously high value slows it down, and any value higher than System.Int32 can store will cause an error.

answered Sep 1, 2023 at 7:03

garethTheRed

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