Powershell - Capture and display PREVIOUS line when string match = true

Question

I have a script that captures and displays the line of a string match. Very simple. What I need now is the previous line to be displayed. I may need the previous few lines but for now my task is to just capture and display the previous line once a string match is found.

Here is my current script. I have no clue how to alter it for my purposes. Any help is appreciated.

$searchWords="NEW", "CATLG", "DELETE"


# List the starting (parent) directory here - the script will search through every file and every sub-directory - starting from the one listed below  
Get-Childitem -Path "C:\src\" -Include "*.job"  -Recurse | 
  Select-String -Pattern $searchWords | 

# the output will contain the [Found] word, the document it found it in and the line contents/line number containing the word
    Select Filename,Line,@{n='SearchWord';e={$_.Pattern}}, LineNumber

Do you want the previous line in a separate property/column in the output? — Mathias R. Jessen, Sep 01 '22 at 14:21
Does this answer your question? [PowerShell: Select line preceding a match -- Select-String -Context issue when using input string variable](https://stackoverflow.com/questions/44682017/powershell-select-line-preceding-a-match-select-string-context-issue-when-u) — Renat, Sep 01 '22 at 14:25
I do not need to separate them by a column or anything like that. Just have them print on the screen. — user3166462, Sep 01 '22 at 14:47

mklement0 · Accepted Answer · 2022-09-01T15:03:06.623

Add -Context 1 to your Select-String to also capture 1 line before each matching line.
In your Select-Object (a built-in alias of which is select), replace property name Line with a calculated expression that retrieves that line via the .Context.PreContext property of the [Microsoft.PowerShell.Commands.MatchInfo] instances that Select-String outputs:

Get-Childitem -Path "C:\src" -Include "*.job"  -Recurse | 
  Select-String -Context 1 -Pattern $searchWords | 
  Select-Object Filename,
                @{n='LineBefore';e={$_.Context.PreContext[0]}},
                @{n='SearchWord';e={$_.Pattern}},
                LineNumber

Note:

-Context accepts two arguments: the first one specifies how many lines to capture before, and the second for how many to capture after; e.g., -Context 1, 2 captures one line before, and 2 lines after each match, reflected as arrays of strings in .Context.PreContext and .Context.PostContext, respectively.
-Context only works meaningfully with line-by-line input:
- When you specify files for Select-String to search through:
  - Either: By providing [System.IO.FileInfo] instances such as via Get-ChildItem, as in your case.
  - Or: By using Select-String's own -Path or -LiteralPath parameter (which doesn't support recursion, however)
- When you provide individual lines as input, such as via an array (stream) of lines (as opposed to a multi-line string).
  - Note that while Get-Content (without using -Raw) does provide a stream of lines, it is much faster to use Get-ChildItem to pipe a [System.IO.FileInfo] instance describing that file instead.

Powershell - Capture and display PREVIOUS line when string match = true

1 Answers1