Escape characters, Delimiters and Quotes

The PowerShell escape character is the grave-accent(`)

The escape character can be used in three ways:

1) When used at the end of a line, it is a continuation character - so the command will continue on the next line.

2) To indicate that the next character following should be passed without substitution. For example $myVariable will normally be expanded to display the variables contents but `$myVariable will just be passed as $myVariable

3) When used inside double quotation marks, the escape character indicates that the following character should be interpreted as a 'special' character.

Special characters

Special characters are used to format/position string output.

   `0  Null
   `a  Alert bell/beep
   `b  Backspace
   `f  Form feed (use with printer output)
   `n  New line
   `r  Carriage return
 `r`n  Carriage return + New line
   `t  Horizontal tab
   `v  Vertical tab (use with printer output)

Using the Escape character to avoid special meaning.

   ``  To avoid using a Grave-accent as the escape character
   `#  To avoid using # to create a comment
   `'  To avoid using ' to delimit a string
   `"  To avoid using " to delimit a string

When setting a string variable the # character does not need to be escaped, but at the command line # will act as a comment unless escaped:

PS C:\> echo 1 # 1
1
PS C:\> echo 1 `# 1
1
#
1

The escaped quotes allow quotation marks to be displayed on screen rather than being interpreted as the start or end of a string. The same effect can also be achieved by doubling-up the quote marks: "" or ''
For powershell.exe, the horizontal tab stops are every 8th character.

Examples

PS C:\> Write-Host "First Line `nSecond line"
First Line
Second Line

PS C:\> "12`t90`n1234567890"
 12      90
 1234567890

PS C:\> Write-Host "Header1`tHeader2 `n123.45`t600"
 Header1  Header2
 123.45   600

PS C:\> "`a `a"
<Two audible beeps are produced.>

Quotation Marks

Either single or double quotes may be used to specify a literal string.

Single-Quoted Strings (')
When you enclose a string in single quotation marks, any variable names in the string such as '$myVar' will appear exacly as typed when the command is processed. Expressions in single-quoted strings are not evaluated, not even escape characters or any of the Special characters listed above. If the string contains any embedded single quotes, they must be doubled (replace ' with '')

$msg = 'Every "lecture" should cost $5000'

Double-Quoted Strings (")
When you enclose a string in double quotation marks, any variable names in the string such as "$myVar" will be replaced with the variable's value when the command is processed. You can prevent this substitution by prefixing the $ with an escape character. Any embedded double quotes can be escaped `" or doubled (replace " with "")

$msg = "Every ""lecture"" should cost `$5000"
$msg = "Every 'lecture' should cost `$5000"
$var = 45

"The value of " + '$var' + "is '$var'"
"The value of `$var is '$var'"
$query = "SELECT * FROM Customers WHERE Name LIKE '%JONES%'"

Verbatim arguments --%

In PowerShell 3.0 the special marker --% is a signal to PowerShell to stop interpreting any remaining characters on the line. This can be used to call a non-PowerShell utility and pass along some quoted parameters exactly as is.

for example instead of escaping every character that PowerShell may interpret:
PS C:\> FIND.EXE '"Search Text"' "C:\Program Files `(x86`)\Demo\text.txt"
we can instead use:
PS C:\> FIND.EXE --% "Search Text" "C:\Program Files (x86)\Demo\text.txt"

Any PowerShell variables after the --% won’t be expanded but you can work around this by building up the command string using more than one variable:

$command = 'FIND.EXE --%'
$params = "C:\Program Files (x86)\Demo\text.txt"

& $command "Search Text" $params;

If the command type is Application, the parameter --% is not passed to the command. The arguments after --% have any environment variables (strings surrounded by %) automatically expanded. For example:
PS C:\> FINDSTR.EXE --% "%ProgramFiles%"
In the above %ProgramFiles% is replaced with the value $env:ProgramFiles

Concatenating Strings

Concatenate strings with +
In many cases, when combining simple strings, the + operator is not needed:
PS C:\> $first = "abcde"
PS C:\> $second = "FGHIJ"
PS C:\> "$first $second"
abcde FGHIJ

but when combining more complex objects, the + operator becomes very useful:
For example if we retrieve an environment variable  
$drive = gci env:SystemDrive
This returns a DictionaryEntry object with .name and .value properties.

# Adding this to a string will give the wrong result
PS C:\> "aaa $drive bbb"
aaa System.Collections.DictionaryEntry bbb

# Concatenating it with a string is closer, but still wrong:
PS C:\> "aaa " + $drive + " bbb"
aaa System.Collections.DictionaryEntry bbb

# Specify the .value property and concatenate that with + to get the desired result:
PS C:\> "aaa " + $drive.value + " bbb"
aaa C: bbb

# Alternatively use the $( ) SubExpression operator:
PS C:\> "aaa $($drive.value) bbb"
aaa C: bbb


(an easier method would be using $drive = $env:SystemDrive which will return a system.string in the first place.)

Backslash \

In many programming languages including C# (.Net) and most UNIX shells the escape character is \

PowerShell is a Windows shell, and Windows already uses the backslash as a path separator C:\Windows\….

In Windows CMD the escape character is ^ although this was not a great choice as ^ is a valid character in NTFS filenames.

The PowerShell designers could have adopted the forward slash as a path separator C:/Windows/… , and then allocated the backslash as the escape character but this would have caused huge confusion and so instead they left paths unchanged and allocated ` as the escape character.

The backtick ` is a valid character in NTFS filenames, so should you encounter one in a filename, it will need to be escaped.

In some PowerShell expressions (matching operations) a backslash character will be interpreted as the start of a Regular Expression, (e.g. \w = match word)
To escape this and treat the backslash as an ordinary character, double it (replace \ with \\ )

Here strings

A here string is a single-quoted or double-quoted string which can span multiple lines.
Expressions in single-quoted strings are not evaluated.

All the lines in a here-string are interpreted as strings, even though they are not enclosed in quotation marks.

$myHereString = @'
some text with "quotes" and variable names $printthis
some more text
'@


$anotherHereString = @"
The value of `$var is $var
some more text
"@

Inside a here-string, double and single quotes are not special but quoted literally, all line breaks are preserved.

The @ character is also used to create arrays, create hash tables and as a splat operator.

“Be not angry that you cannot make others as you wish them to be, since you cannot make yourself as you wish to be” - Thomas A Kempis

Related:

Bug report - Executing commands which require quotes and variables is practically impossible.
Escaping Distinguished Names - Richard L. Mueller
Using PowerShell to run old command line tools - Jose Barreto
Invoke-Expression - Run a PowerShell expression
Join-Path - Combine a path and child-path
Pipelines - Pass objects down the pipeline
Variables - PowerShell Variables (int, String)


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