PowerShell RegEx

'the goose' -match 'g[oe]{2}se'    # true

Escaping

'f\d.' -match [regex]::escape('\d.')

Capture groups:

'the goose' -match 'g([oe]{2})s(e)'
$Matches[1]

The automatic variable $Matches is a hashtable with the captured text. Key 0 holds the entire match.

> $Matches

Name                           Value
----                           -----
2                              e
1                              oo
0                              goose

Note that the hashtable contains only the first occurrence of any matching pattern. e.g. the goose geese → goose only (docs)

Named Captures: use ?<keyname>, e.g. (?<keyname>pattern) :

'some geese flew south' -match '(?<bird>g[oe]{2}se) fl(?<tense>ew|y) (?<dir>\w+)'

> $Matches

Name                           Value
----                           -----
tense                          ew
bird                           geese
dir                            south
0                              geese flew south

Find/Replace

> 'red fox, brown fox, white swan' -replace '\w+ fox','pooh bear'

pooh bear, pooh bear, white swan

$& : all matched text

> 'quick fox, quack fox, a quick quack fox' -replace 'qu\w+','$& $&'

quick quick fox, quack quack fox, a quick quick quack quack fox

With captures:

> '1 red fox, 2 brown bears, 3 white swans' -replace
    '(\d) (\w+) (?<animal>([^s\W]|s\w)+)s?',
    '${animal} x$1 ($2)'

fox x1 (red), bear x2 (brown), swan x3 (white)

Special rules for using $ since it’s used in string expansion: docs (summary)

Using $ in general: use literal strings ''

$ as a literal: use $$ – e.g. '5.99' -replace '(.+)','CAD$$$&' → CAD$5.99

If not using literal strings, escape the $, i.e. "`$1" and "`$`$"

$m = 'the goose geese' | sls -pattern 'g([oe]{2})se'
$m.matches.groups[1]

> $m.matches

Groups   : {0, 1}
Success  : True
Name     : 0
Captures : {0}
Index    : 0
Length   : 5
Value    : goose

# capture groups
> $m.matches.groups[1]

Success  : True
Name     : 1
Captures : {1}
Index    : 1
Length   : 2
Value    : oo

ref docs