{"id":2071,"date":"2015-08-12T00:00:00","date_gmt":"2015-08-11T00:00:00","guid":{"rendered":"https:\/\/test.simple-talk.com\/uncategorized\/when-to-quote-in-powershell\/"},"modified":"2016-07-28T10:47:58","modified_gmt":"2016-07-28T10:47:58","slug":"when-to-quote-in-powershell","status":"publish","type":"post","link":"https:\/\/www.red-gate.com\/simple-talk\/sysadmin\/powershell\/when-to-quote-in-powershell\/","title":{"rendered":"When to Quote in PowerShell"},"content":{"rendered":"
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\tWhen do you need to use quotes or not in PowerShell? And when you need them, do you need single quotes or double quotes? At first glance, you would think that PowerShell’s own help page about_Quoting_Rules<\/a> would answer both of those, but it does not! It covers part of the topic, primarily string interpolation<\/em> and here strings<\/em> (both of which we’ll discuss below). In other words, it assumes you need quotes and then explains some of the factors affecting which-single or double-to choose. But it completely ignores the bigger picture. Meanwhile over on StackOverflow you will find When do I need to use quotes in PowerShell?<\/a> That poses the canonical question yet barely lands a glancing blow on the answer. So, this article is here to bring together the entire topic of quoting in PowerShell in one place for a handy reference source. <\/p>\n

Do You Need Quotes?<\/h2>\n

\tLet’s start with an example. Consider listing the details of a couple files with the Get-ChildItem<\/strong> cmdlet-I use its ls<\/strong> alias to minimize the presence of the cmdlet name, focusing just on the elements that we are quoting or not. Which of these is valid PowerShell and lists the details of the two files in question? <\/p>\n

\"a.txt\", \"b.txt\" | ls\t# A\na.txt, b.txt | ls\t# B\nls \"a.txt\", \"b.txt\"\t# C\nls a.txt, b.txt\t        # D<\/pre>\n
 \tThe answer is (A), (C), and (D); assuming the appropriate files exist, all of those return the exact same result (they will give different error messages if the files do not exist). Because both cases (C) and (D) work correctly, you can infer that when the cmdlet is given first, you do not need quotes but you may use them. So let’s focus on the two primordial cases: case (A) where quotes are needed and case (D) where quotes are not needed: <\/p>\n
\"a.txt\", \"b.txt\" | ls\t# A\nls a.txt, b.txt\t        # D<\/pre>\n
 \tTo understand the difference requires an awareness of PowerShell’s two parsing modes, command parsing<\/em> and execution parsing<\/em>. These two modes work together to allow PowerShell as a scripting<\/em> language to peacefully co-exist with PowerShell as a shell<\/em> language allowing you, the user, to be able to move code between a script and the command line and have it just work. That is, in a script (program) having to type string literals with quotation marks like this… <\/p>\n
rm \"a.txt\", \"b.txt\", \"c.txt\"<\/pre>\n
 \tis quite reasonable. However, at the command line that would be annoying to some, intolerable to others. You should be able to just type this: <\/p>\n
rm a.txt, b.txt, c.txt<\/pre>\n
 \tFurthermore, like any good shell, you must be able to type expressions like 5 + 2<\/strong> and get a response of 7<\/strong>, or type “hello world”<\/strong> and get hello world<\/strong> echoed back. Yet when you type a cmdlet name, e.g. Get-Process<\/strong>, it should execute the command, not just echo the characters “<\/strong>Get-Process<\/strong>“<\/strong>. Simple, you say, because omitting the quotes signals that it is a command to execute, right? But what if you want to execute a command with a space in it, perhaps C:\\Program Files\\<\/strong>xyz.exe<\/strong> ? Well, without quotes PowerShell would just try to execute C:\\Program<\/strong> with Files\\xyz.exe<\/strong> as its first argument. So clearly it must have quotes because of the space, but if you try “C:\\Program Files\\xyz.exe<\/strong>” it just gets echoed back. Whew! <\/p>\n
 \tPowerShell’s two parsing modes allow you to untangle and manage your commands and your scripts with ease. Per Keith Hill’s reference article, Understanding PowerShell Parsing Modes<\/a>: <\/p>\n
 \t“First [you] need to parse like a traditional shell where strings (filenames, dir names, process names, etc.) do not need to be quoted. Second [you] need to be able to parse like a traditional language where strings are quoted and expressions feel like those you would find in a programming language. In PowerShell, the former is called Command parsing mode and the latter is called Expression parsing mode. It is important to understand which mode you are in and more importantly, how you can manipulate the parsing mode.” <\/p>\n
 \tThe rules for selecting a mode (or determining which you are in) are simple: <\/p>\n