PowerShell: find line but include proceeding and preceding line(s)

Question

This is a conceptual question that I have only briefly thought through my head. I have idea how I might do it but it seems more complicated than I think I will make it out to be.

A common need is for searching through a file (e.g. may be an error log) and I want to search that file for one particular string value. However in my case I thought some applications output an error on one line but the line that includes the error text could be on the proceeding or preceding line of that log (e.g. SQL Server error logs). So in this case I might want to include the line found with the specific string provided in the search, but include the line (or even lines) before and after it.

I try to keep my scripts as simple as I can for readability of others that may use it or find it. I cannot think in my head this would be to easily written.

EDIT

Based on the answer provided using Select-String this is an example of what I am attempting to do:

[void][System.Reflection.Assembly]::[LoadWithPartialName]('Microsoft.SqlServer.SMO')
$s = New-Object Microsoft.SqlServer.Management.Smo.Server MyServer
$s.EnumErrorLogs() | select -ExpandProperty Name | 
foreach { $s.ReadErrorLog($_) | select-string -Pattern "*Serverity: 25*" -Context 3 -SimpleMatch | 
select LogDate, ProcessInfo, Text

Solution

The Select-String cmdlet with -Context is pretty much a perfect match for what you're trying to do... This will read the contents of a file and search for a string, returning the 3 lines above and below the string:

$file = C:\Users\Public\Documents\log.txt
$string = "*error*"
Get-Content $file | Select-String $string -Context 3 -SimpleMatch

By default Select-String uses regular expressions, but -SimpleMatch will do a plain text search.

Comments

[Admin]

Rereading my own question, it I a bit weak...I'd even down vote it myself.

[Tim Ferrill]

It might help if you spelled "Severity" correctly... Just sayin. :)

[Admin]

I actually can't get this to work dealing with reading SQL Server error logs. I am reading them via SMO so don't know if that effects it, wouldn't think it would.

[Tim Ferrill]

Select-String is looking for a contiguous string, not object attributes. You might have to convert each line to a string and then back to columns in order to achieve the desired result. You might also post some of the output you're getting from SMO...

[Admin]

That sounds to be more trouble than it is worth as I am trying to just keep this function as simple as possible. As I expect you are correct on the object property I think I will just pass on trying to add this functionality.

[Jorge Luque]

Is there a way to only show preceding lines but not the lines after?