PowerShell Nested Here-String

Question

Placing the following within a script will fail:

$MyString = @'
hello
@'
'@
bye
'@

write-host $MyString

The error returned is as follows:

At C:\scripts\test.ps1:6 char:1
+ '@
+ ~~
The string is missing the terminator: '.
    + CategoryInfo          : ParserError: (:) [], ParseException
    + FullyQualifiedErrorId : TerminatorExpectedAtEndOfString

Prefixing the nested @' and '@ with a backtick (grave accent) does serve as an escape character, however it is also treated as literal, and therefore appears in the output of $MyString.

Is there a correct way to escape a single quoted here-string within a single quoted here-string that does not interfere with the output?

NB:

I should have mentioned that the content of the outer here-string is dynamically populated, the content is supplied by another program to the powershell script as a command line argument. This is not reflected in the sample code as I didn't want to cloud the question with my very specific and somewhat niche implementation.

It's not all that likely that the outer here-string will contain an inner here-string (but it could happen), therefore I feel that some defensive programming is warranted in order to accommodate such an occurrence.

Answer 1

Use double quotes, either for the outer here-string:

$MyString = @"
hello
@'
'@
bye
"@

or for the inner here-string:

$MyString = @'
hello
@"
"@
bye
'@

Answer 2

Try a ScriptBlock (enclosed in {}) instead of the outer Here-String. It works for the original example:

$MyString = {
hello
@'
'@
bye
}
write-host $MyString

Result:

PS > $MyString = {
>> hello
>> @'
>> '@
>> bye
>> }
>> write-host $MyString
>>

hello
@'
'@
bye

PS >

Note the extra blank lines at the beginning and the end. You can avoid them if you omit the line breaks after { and before }.

You may explicitly convert the ScriptBlock to a String with the ToString() function, if necessary.

Not sure if this workaround works in any use case, but it looks fairly clean, because the ScriptBlock takes all content without interpretation and is not confused by any curly braces nor is it interested in any quotes.

Answer 3

Regardless of whatever here-string quote character you choose, there is always the powershell escape character, the backtick

$MyString = @"
hello
@`'
`'@
bye
"@

is equivalent to

$MyString = @'
hello
@`'
`'@
bye
'@

If you need to esccape a backtick, just put 2 of them

Write-Host @"

here is a backtick ``

"@