How to enter a multi-line command

Question

Is it possible to split a PowerShell command line over multiple lines?

In Visual Basic I can use the underscore (_) to continue the command in the next line.

Answer 1

You can use a space followed by the grave accent (backtick):

Get-ChildItem -Recurse `
  -Filter *.jpg `
  | Select LastWriteTime

However, this is only ever necessary in such cases as shown above. Usually you get automatic line continuation when a command cannot syntactically be complete at that point. This includes starting a new pipeline element:

Get-ChildItem |
  Select Name,Length

will work without problems since after the | the command cannot be complete since it's missing another pipeline element. Also opening curly braces or any other kind of parentheses will allow line continuation directly:

$x=1..5
$x[
  0,3
] | % {
  "Number: $_"
}

Similar to the | a comma will also work in some contexts:

1,
2

Keep in mind, though, similar to JavaScript's Automatic Semicolon Insertion, there are some things that are similarly broken because the line break occurs at a point where it is preceded by a valid statement:

return
  5

will not work.

Finally, strings (in all varieties) may also extend beyond a single line:

'Foo
bar'

They include the line breaks within the string, then.

Answer 2

I just found out that there must not be any character between the back tick and the line break. Even whitespace will cause the command to not work.

Answer 3

In most C-like languages I am deliberate about placing my braces where I think they make the code easiest to read.

PowerShell's parser recognizes when a statement clearly isn't complete, and looks to the next line. For example, imagine a cmdlet that takes an optional script block parameter:

    Get-Foo { ............ }

if the script block is very long, you might want to write:

    Get-Foo
    {
        ...............
        ...............
        ...............
    }

But this won't work: the parser will see two statements. The first is Get-Foo and the second is a script block. Instead, I write:

    Get-Foo {
        ...............
        ...............
        ...............
    }

I could use the line-continuation character (`) but that makes for hard-to-read code, and invites bugs.

Because this case requires the open brace to be on the previous line, I follow that pattern everywhere:

    if (condition) {
        .....
    }

Note that if statements require a script block in the language grammar, so the parser will look on the next line for the script block, but for consistency, I keep the open brace on the same line.

Simlarly, in the case of long pipelines, I break after the pipe character (|):

    $project.Items | 
        ? { $_.Key -eq "ProjectFile" } | 
        % { $_.Value } | 
        % { $_.EvaluatedInclude } |
        % {
            .........
        }