PowerShell 101, Lesson 4

Most PowerShell statements include string values. Usually, these strings are passed to cmdlets as arguments. In some cases, the strings are enclosed in single quotes. In other cases, they’re enclosed in double quotes. And sometimes they’re not enclosed in quotes at all. It’s important to understand how to properly handle strings. The rules that govern how to do so are often referred to as quoting rules. In this lesson, you’ll learn about these rules. Specifically, you’ll learn when to enclose string values in quotes and whether to use single or double quotes. In addition, you’ll learn how to flag, or escape, special characters.

Working with String Values
Whenever you enclose text in quotes, PowerShell treats that text as a string value. So, as long as the text doesn’t contain any special characters (you’ll learn more about these characters shortly) or reference variables (I’ll discuss how to reference variables in strings in the next lesson), you can enclose the text in either single or double quotes. For example, the following statements achieve the same results:

Write-Output “String in quotes.”

Write-Output ‘String in quotes.’

In these examples, the Write-Output cmdlet sends a string object down the pipeline or, in this case, directly to the PowerShell console. As you can see in Figure 1, the outputted value is the same for both statements.

In addition to the Write-Output cmdlet, PowerShell’s Out-Host and Write-Host cmdlets output information to the console. Their differences lie in the details. For example, the Write-Output cmdlet sends output down the pipeline to the next cmdlet. When Write-Output is the last cmdlet in the pipeline, the output is displayed in the console. The Out-Host cmdlet sends output directly to the console and offers an optional parameter that lets you view the output one screen at a time, which can be helpful if there is a lot of output. This is the default output cmdlet, so if you don’t specify an output cmdlet, Out-Host cmdlet is used. The Write-Host cmdlet also sends output directly to the console. However, Write-Host has two optional parameters that let you change the color of the text or text background, thereby creating a customized console.

For basic quoted string values that you want to output directly to the console window, all three cmdlets behave in similar ways. For example, the following four commands all display the string in the console window in the same way as in Figure 1:

“String in quotes.”

Write-Output “String in quotes.”

Write-Host “String in quotes.”

Out-Host `
  -InputObject “String in quotes.”

Notice that no cmdlet is specified in the first command. As a result, the Out-Host cmdlet is used.

For many of the examples in this lesson, I use the Write-Output cmdlet because it outputs an object in a way similar to many other cmdlets. This lets me demonstrate different principles about quoted values. Keep in mind, however, that the Write-Output, Out- Host, and Write-Host cmdlets can behave differently in different circumstances. For more information about these cmdlets, see their Help files.

If you want to include quotes within a string, you can use single quotes within double quotes or double quotes within single quotes:

Write-Output “String ‘in’ quotes.”

Write-Output ‘String “in” quotes.’

If you refer again to Figure 1, you’ll see that inside quotes in both cases are carried to the output. This isn’t the case when you use the same type of quotes throughout the string:

Write-Output “String “in” quotes.”

Write-Output ‘String ‘in’ quotes.’

As Figure 1 shows, the results are quite different. In both cases, the quotes are not displayed and a new line is added. This is because PowerShell interprets the one string as multiple strings and consequently adds a line break. For example, PowerShell interprets String as the first string (so it adds a line break after that string), then interprets the rest as a different string. You can use double quotes within double quotes, but you must escape the inside quotes, which I’ll describe how to do later.

Whenever you work with quotes, be careful not to mix up the type of quotes or forget to include one. Otherwise, you might get stuck in a loop that continues to prompt you for an entry—but nothing you enter gets you out of the loop. If you run into that situation, press Ctrl+C to return to the command prompt.

Another issue to take into account when defining cmdlet arguments is how Power- Shell treats numerical values. As I said earlier, PowerShell treats any values within quotes as strings, even if the value consists of all numbers:

Write-Output “123”

When you execute this statement (shown in Figure 2), the value returned is a string object, as Figure 2 shows. You can verify the value’s type by running the statement:

(Write-Output “123”).GetType()

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