How do parse this string in Powershell?

Question

I have a block of text I need to parse (saved in a variable) but I'm unsure how to go about it. This block of text, saved in a variable we can call $block for simplicity's sake, includes all the whitespace shown below.

I would like the result to be an iterable list, the first value being Health_AEPOEP_Membership_Summary - Dev and the second one being Health_AEPOEP_YoY_Comparison_Summary - Dev. Assume this list of workbooks can be longer (up to 50) or shorter (minimum 1 workbook), and all workbooks are formatted similarly (in terms of name_with_underscores - Dev. I'd try the $block.split(" ") method, but this method gives many spaces which may be hard to enumerate and account for.


                    Workbooks : Health_AEPOEP_Membership_Summary - Dev [Project: Health - Dev]
                                Health_AEPOEP_YoY_Comparison_Summary - Dev [Project: Health - Dev]

Any help is much appreciated!

You will learn everything you need when you watch this video: Sophisticated Techniques of Plain Text Parsing — Olaf
– Olaf, Commented Nov 18, 2020 at 18:18

Mathias R. Jessen · Accepted Answer · 2020-11-18 22:15:01Z

1

You could write a multi-line regex pattern and try to extract the names, but it might be easier to reason about if you just breaking it into simple(r) steps:

$string = @'

                    Workbooks : Health_AEPOEP_Membership_Summary - Dev [Project: Health - Dev]
                                Health_AEPOEP_YoY_Comparison_Summary - Dev [Project: Health - Dev]



'@

# Split into one string per line
$strings = $string -split '\r?\n'

# Remove leading whitespace
$strings = $strings -replace '^\s*' 

# Remove `Workbooks : ` prefix (strings that don't match will be left untouched)
$strings = $strings -replace '^Workbooks :\s*' 

# Remove `[Project $NAME]` suffix
$strings = $strings -replace '\s*\[Project: [^\]]+\]'

# Get rid of empty lines
$strings = $strings |Where-Object Length

$strings now contains the two project names

edited Nov 18, 2020 at 22:15

answered Nov 18, 2020 at 18:27

Mathias R. Jessen

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3 Comments

Olaf Over a year ago

And I've heard SO should not be a free code writing service. ;-)

Ameera Khan Over a year ago

when i run this, the [Project...] text remains. Why is that?

Mathias R. Jessen Over a year ago

@AmeeraKhan There was a typo in the regex pattern (I forgot to escape the [), I've updated it now

Doug Maurer · Accepted Answer · 2020-11-18 18:48:12Z

1

If the text is in a file it would make this a little easier, and I would recommend this approach

switch -Regex -file ($file){
    '(\w+_.+- Dev)' {$matches.1}
}

Regex details

() - capture group

\w+ - match one or more letter characters

_ - match literal underscore

.+ - match one or more of any character

- Dev - literal match of dash space Dev

If it's already in a variable, it would depend if it's a string array or a single string. Assuming it's a single string, I'd recommend this approach

$regex = [regex]'(\w+_.+)(?=(\s\[.+))'

$regex.Matches($block).value

Health_AEPOEP_Membership_Summary - Dev
Health_AEPOEP_YoY_Comparison_Summary - Dev

Regex details

Same as above but added the following

(?=) - Look ahead

\s\[.+ - match a space, a left square bracket, one or more characters

Simply add a variable assignment $strings = before either of these to capture the output. Either would work on one or 500 workbooks.

edited Nov 18, 2020 at 18:48

answered Nov 18, 2020 at 18:19

Doug Maurer

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1 Comment

Ameera Khan Over a year ago

Hmm... when I run the second option, it seems like the [Project...] portion remains. When I run the first suggestion, only the ] character is removed, not everything else within brackets. Why would that be? EDIT: the first solution works when I add a space after the - Dev in the regex expression.

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