Regular expressions are used for pattern matching against strings. They can be used multiple ways, the most common being to check if a string contains some pattern, or to extract some text which matches a pattern. In this instance we're doing the latter.
if ($output -match 'Netmask:\s*(.*)\b') {
$matches
$spStatus.Netmask = $matches[1]
} else {
$spStatus.Netmask = "unknown"
}The first line checks to see if the string $output matches against the regular expression 'Netmask:\s*(.*)\b'. If it matches it goes into the if statement. Breaking out the regex used, there's a couple of things going on...
# look for the text "Netmask:" (no quotes, but colon required)
Netmask:
# followed by any number of white space characters, e.g. tab or space
# the \s is short for whitespace, the * is short for 0 or more
\s*
# capture any text after the last white space character
# the parenthesis denotes "capture text", the period is short for any character,
# and the * is short for any number of occurrences
(.*)
# stop capturing at the end of the word. \b is short for "word boundary"
\b
Assuming it matches the regex, the extracted text will be found in a created array variable, $matches, with the first value ($matches[0]) being equal to the whole of the matched text, and the second and later values ($matches[1], etc.) equal to the extracted values.
There is a huge amount of information on regex out there. There's a decent reference of the special quantifiers and identifiers here. Regex can be complicated, but they've been around for a long time (Perl uses them heavily), so for most things you can search the internet and find an example or two to base yours off of.
Hope that helps.
Andrew
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