Split string with PowerShell and do something with each token

"Once upon a time there were three little pigs".Split(" ") | ForEach {
    "$_ is a token"
 }

The key is $_, which stands for the current variable in the pipeline.

About the code you found online:

% is an alias for ForEach-Object. Anything enclosed inside the brackets is run once for each object it receives. In this case, it's only running once, because you're sending it a single string.

$_.Split(" ") is taking the current variable and splitting it on spaces. The current variable will be whatever is currently being looped over by ForEach.

-split outputs an array, and you can save it to a variable like this:

$a = -split 'Once  upon    a     time'
$a[0]

Once

Another cute thing, you can have arrays on both sides of an assignment statement:

$a,$b,$c = -split 'Once  upon    a'
$c

a

To complement Justus Thane's helpful answer:

• As Joey notes in a comment, PowerShell has a powerful, regex-based -split operator.

  • In its unary form (-split '...'), -split behaves like awk's default field splitting, which means that:
    • Leading and trailing whitespace is ignored.
    • Any run of whitespace (e.g., multiple adjacent spaces) is treated as a single separator.

• In PowerShell v4+ an expression-based - and therefore faster - alternative to the ForEach-Object cmdlet became available: the .ForEach() array (collection) method, as described in this blog post (alongside the .Where() method, a more powerful, expression-based alternative to Where-Object).

Here's a solution based on these features:

PS> (-split '   One      for the money   ').ForEach({ "token: [$_]" })
token: [One]
token: [for]
token: [the]
token: [money]

Note that the leading and trailing whitespace was ignored, and that the multiple spaces between One and for were treated as a single separator.