Checking for a substrings in an array of strings

Question

I'm on a project where I need to match a string for a certain substring within a text file. I'm using PowerShell. I found this, and this gave me a great start.

Check if a string contains any substring in an array in PowerShell

From this, I've been able to find a single substring in a single string, and have been trying (see below) to extend this to finding several substrings in an array of strings. The array of strings are column names in a DB table; I need to compare these to data in a text file, where each line (in the text file) will an entry in the DB. To futher clarify, here are two lines of code that I'm using:

$columnNames = ("Col_1","Col_2","Col_3","Col_4","Col_5")
$fileData = Get-Content dataRetrieved.txt

The text file (dataRetrieved.txt) contains data shown below, but only a small part of the data is left-justified; I could not figure out how to correctly illustrate how it appears in a text editor.:

Col_1=this is some type of data

Col_2=more stuff that was collected

Col_3=even more data that might continue on another line and probably indented

Col_5=ABCDEFG123

Col_1=Some more stuff

Col_2=yada yada

EDIT: Example of this file:

Col_1=this is some type of data
 Col_2=more stuff that was collected

Col_3=even more lines of data
     that continues on another
     Col_5=ABCDEFGi23
  Col_1=Some more stuff
Col_2=yada yada
...

Note #1: there will be "irregularities" in the text file - no control over how the users input the data.

Note #2: there is no limit to how many lines in the text file

Note #3: there may/may not be values foreach of $columnNames

BIG NOTES:

I'm a standard user on the system, and cannot install/configure any software/packages

The system admins will not install anything

From a programming standpoint I have PowerShell, Java (somewhat limited, e.g. no JDBC, nor will it be installed)

Code that I have tried:

$columnNames = ("Col_1","Col_2","Col_3","Col_4","Col_5")
$fileData = Get-Content dataRetrieved.txt
for ($k=0;$k -lt $columnNames.Count;$k++) {
    if ([bool]($fileData[$k] -match $columnNames[$k])) {
        #code to process the "match"
    }
}

What I'm seeing doesn't make sense to me. Outside of the for loop, statements like $columnNames[0] or $fileData[0] will give me what I believe to be the correct data. Inside the for loop, both $columnNames[$k] and $fileData[$k] give me the entire array.

Appreciate any/all help.

Can you add some more details on the contents of this dataRetrieved.txt file ? (see my mis-use of the answer component of SO ) — Luuk
– Luuk, Commented Sep 12, 2023 at 15:18
"the entire array" What you you mean? $columNames[3] (when $k=3) should return "Col_4" and not an entire array — Luuk
– Luuk, Commented Sep 12, 2023 at 16:10
@Solaris_Guy: You could use edit to correct the typo .... (Thanks!) — Luuk
– Luuk, Commented Sep 12, 2023 at 17:26

Doug Maurer · Accepted Answer · 2023-09-12 16:09:31Z

I would use a regex pattern for all desired match criteria with a named capture group.

# the parenthesis was not needed around this list
$columnNames = "Col_1","Col_2","Col_3","Col_4","Col_5"

# create a single multi value pattern. Will look like this (?<Column>Col_1|Col_2|Col_3|Col_4|Col_5)
$pattern = '(?<Column>{0})' -f ($columnNames -join '|')

# just as an example we'll write out the specific column that matched
# followed by the line that matched. 
foreach($line in $filedata){
    if($line -match $pattern){
        Write-Host The column that matched is $matches.column
        Write-Host The line that matched is $line
    }
}

Output with your sample data

The column that matched is Col_1
The line that matched is Col_1=this is some type of data
The column that matched is Col_2
The line that matched is  Col_2=more stuff that was collected
The column that matched is Col_3
The line that matched is Col_3=even more lines of data
The column that matched is Col_5
The line that matched is      Col_5=ABCDEFGi23
The column that matched is Col_1
The line that matched is   Col_1=Some more stuff
The column that matched is Col_2
The line that matched is Col_2=yada yada

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