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PowerShell Parsing Name and Version out of a String

I want to parse the name and the version of a string.

The schema of the string is the following:

EntityFramework.6.2.0

EntityFramework.Functions.1.4.1

What I want to have is an array or an object with the name of the package and the version.

The version number can have 1,2,3 or 4 digits and the name can also have "."

$version = @()
$name = @()

"EntityFramework.Functions.1.4.1".Split('.') | %
if ($_ -match "^d+$")
$version += $_
else
$name += $_



$name -join "."
$version -join "."


This works but I think there is a better way to do it.

Any Idea to short this snippet or make it more smart.

3 Answers
3

This can be improved by just relying on regex from the start:

$null = 'EntityFramework.Functions.1.4.1' -match '(?<name>[^d]+)(?<version>d.+)'
$name, $version = $Matches['name'].TrimEnd('.'), [version]$Matches['version']

$name
>> EntityFramework.Functions

$version
>> Major Minor Build Revision
>> ----- ----- ----- --------
>> 1 4 1 -1


Explained:

( // Capture a group
?<name> // Name it "name"
[^d]+ // Capture until you find a digit
) // End capture group

( // Capture a group
?<version> // Name it "version"
d.+ // Start at a digit and wildcard catch everything after
) // End capture group


Shortened (for haxxorz):

if ('EntityFramework.Functions.1.4.1' -match '(.*?(?=.d)).(.+)')

$name, [version]$version = $matches[1, 2]



(gottagoshort):

$name,$version='EntityFramework.Functions.1.4.1'-split'(?<=[^d]).(?=d)'


if

Note: This is an optimized variation of the original answer below, courtesy of TheIncorrigible1.

By using the -split operator with a separator regex that uses lookaround assertions, it is possible to split the string in the desired location with a single operation:

-split

# Stores 'EntityFramework.Functions' in $name
# and '1.4.1' in $version
$name, $version = "EntityFramework.Functions.1.4.1" -split '(?<=[^d]).(?=d)'


(?<=[^d]).(?=d) uses a look-behind assertion ((?<=...) and a look-ahead assertion ((?=...)) to provide the desired context for matching the literal . (.):

(?<=[^d]).(?=d)

(?<=...)

(?=...)

.

.

The regex matches the . only if preceded by a character that is not a digit ([^d]) and is followed by a digit, which is where we want to split: between the end of the package name and the start of the version number.

.

[^d]

Regex assertions in general do not capture characters, so that even though the surrounding character are looked at, it is only the . that is considered the separator, ensuring that the tokens on either side of it are returned in full.

.

The result of the -split operation is a 2-element array, whose elements can be assigned to indidvidual variables via a destructuring assignment ($name, $version = ...)

-split

$name, $version = ...

Original answer:

Note: While the regex used below is slightly shorter than the one above, its interplay with -split is actually conceptually more complex, and the solution requires an additional operation to filter out an empty result element (-ne '').

-split

-ne ''

A more concise solution that uses the -split operator with a regex (regular expression):

-split

# Stores 'EntityFramework.Functions' in $name
# and '1.4.1' in $version
$name, $version = "EntityFramework.Functions.1.4.1" -split '^([^d]+).' -ne ''


^([^d]+). starts matching at the start of the string (^) and matches one or more (+) non-digit characters ([^d]) followed by a literal . (.)

^([^d]+).

^

+

[^d]

.

.

This matches EntityFramework.Functions., but, due to enclosing only the part before the trailing . in (...) to form a capture group, only EntityFramework.Functions is returned.

(By default, what the separator regex matches is not returned - after all, you just want the tokens between the separators - but a capture group embedded in the regex can be used to deliberate include part of the separator in the result array).

EntityFramework.Functions.

.

(...)

EntityFramework.Functions

The separator regex is by definition not found again in the input string (because it is anchored at the start of the string with ^, so the remainder of the string - 1.4.1 - is considered the 2nd and only remaining token.

^

1.4.1

-ne '' filters out the empty first element of the resulting array that is a side effect of the string starting with a match of the separator regex expression.

-ne ''

'foo,bar;baz' -split '[,;]'

'foo', 'bar', 'baz'

-split

ne ''

-split

@(
'EntityFramework.6.2.0',
'EntityFramework.Functions.1.4.1'
) | %

[pscustomobject]@
name = $_ -replace '.([0-9]).*([0-9])$'
version = $_ -replace '^([A-Za-z]).*([A-Za-z]).'




This separates each item based on a group of character types.

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