Regular Expressions and Strings

Regular expressions (regex) let you search, match, and transform text using patterns. PowerShell integrates regex directly into its operators.

The -match Operator and $Matches

The -match operator tests if a string matches a regex pattern. When it succeeds, the automatic $Matches hashtable captures the result:

'Server-042' -match 'Server-(\d+)'
$Matches[0]   # Full match: Server-042
$Matches[1]   # First capture group: 042

Use named captures for clearer code:

'admin@contoso.com' -match '(?<user>.+)@(?<domain>.+)'
$Matches.user    # admin
$Matches.domain  # contoso.com

The -replace Operator

-replace uses regex to find and substitute text. Capture groups are referenced with $1, $2, etc.:

'2025-04-07' -replace '(\d{4})-(\d{2})-(\d{2})', '$2/$3/$1'
# Result: 04/07/2025

.NET Regex Methods

For advanced scenarios, use the [regex] .NET class. [regex]::Match() returns a single match, while [regex]::Matches() returns all matches:

$text = 'IPs: 10.0.0.1 and 192.168.1.5'
$pattern = '\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'
[regex]::Matches($text, $pattern) | ForEach-Object { $_.Value }

Common Patterns

| Pattern | Matches |

|---|---|

| \d+ | One or more digits |

| \w+ | Word characters |

| [A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z]{2,} | Email (simplified) |

| \d{1,3}(\.\d{1,3}){3} | IPv4 address |

String Formatting with -f

The -f operator inserts values into placeholders:

'Hello, {0}! You have {1} items.' -f 'Alice', 5
'{0:N2} GB' -f (1073741824 / 1GB)   # 1.00 GB

Here-Strings

Here-strings preserve multi-line text. Use @" "@ for expandable strings or @' '@ for literal strings:

$name = 'World'
$expandable = @"
Hello, $name!
This preserves "quotes" and line breaks.
"@

$literal = @'
No $variables expanded here.
Everything is literal.
'@