Escape string in PowerShell Regex to a regular string - regex

I have a string that contains some regex in, $(=?, Now this string is a password that I need to pass for some application that I'm building.
The code that I'm trying to use is:
$x = 'GIWs#K?hks2v&HKXb$S9=HK*AZN=i!(S?7'
[Regex]::Escape($x)
I've already tried the method with [Regex]::Escape() and it doesn't meet my requirements because I'm trying to insert the string as a password and it replacing the Regex with \.
Perhaps after I'm doing the [Regex]::Escape() should I try to delete the \ that I'm getting from the result of the command?
After running the [Regex]::Escape() this is the result I'm getting when printing the output:
GIWs#K\?hks2v&HKXb=HK\*AZN=i!\(S\?7
I'm trying to achieve the string without the ' \ ' characters but with the Escape function:
GIWs#K?hks2v&HKXb=HK*AZN=i!(S?7

This is not an answer because I don't know what the problem actually is. However, there are some inherent problems with your current attempt to handle the password string. If you use double quotes ("") around a string, PowerShell will interpolate the string inside the quotes. So any alphanumeric characters following an unescaped $, will be considered a variable name during interpolation. If that variable has no value, $variable will be replaced with a null value. You can see this behavior below:
"rt4837s$GT=\"
rt4837s=\
You should use single quotes ('') when quoting string literals (characters that will be left as is). PowerShell will not attempt interpolation when unescaped single quote pairs are encountered unless there is quote nesting. See below:
'rt4837s$GT=\'
rt4837s$GT=\
If you need a regex escaped string, the same rules apply from above and you should use single quotes.
[regex]::escape('dfaseryh$S9=r??*')
dfaseryh\$S9=r\?\?\*
If for any reason, you need to access that string later without the escape characters, then you can use the regex method Unescape().
[regex]::unescape('dfaseryh\$S9=r\?\?\*')
dfaseryh$S9=r??*
Practical Example of Using Regex Replace:
$OriginalString = 'Username = Anonymous; Password = <password>'
$regexReplace = [regex]::Escape('<password>')
$Password = 'GIWs#K?hks2v&HKXb$S9=HK*AZN=i!(S?7'
$OriginalString -replace $regexReplace,($Password -replace '\$','$$$$')
# Output
Username = Anonymous; Password = GIWs#K?hks2v&HKXb$S9=HK*AZN=i!(S?7
In the code above, $OriginalString is just an ordinary string that can be retrieved from any command or set by a coder. It contains a string <password> that we want to replace with a complex password string GIWs#K?hks2v&HKXb$S9=HK*AZN=i!(S?7.
$Password contains the complex password. Since we only care about replacing <password> and are choosing to use regex replace operator -replace, we need a valid regex expression for matching <password>. There is a caveat here though. When using -replace, the $ in the replacement string is used to prefix capture group names. So there can be cases where the literal string has an unintentional replacement. Capture group 0 is always there if there is a match. So $0 will always cause issues without proper escaping. It is probably best to just escape $ regardless.
For the regex match, we use [regex]::Escape('<password>') since we are unsure if <> are special in regex. If there are no special characters, then the string within the regex expression will not be modified. If it does contain special characters, they will be escaped with \.
As a result, <password> is replaced with GIWs#K?hks2v&HKXb$S9=HK*AZN=i!(S?7.
A recap of the syntax is as follows:
'String With Something You Want to Replace' -replace 'Regex Expression to Match String You Want to Replace','Replacement That Is a Literal String With Escaped $'

Related

powershell -replace: surround captured regex group with dollar signs like: $group$

I want to replace strings like url: `= this.url` with url: $url$
I got quite close with this:
(Get-Content '.\file') -Replace "``= this.(\w+)``", "$ `$1$"
with output url: $ url$.
But when I remove extra space then the output breaks.
How can I escape/modify "$`$1$" so that it works?
You can use
-Replace "``= this\.(\w+)``", '$$$1$$'
Note that
The . must be escaped in the regex pattern
'$$$1$$' is a $$$1$$ string that contains:
$$ - a literal single $ char
$1 - the backreference to the first capturing group
$$ - a literal single $ char.
Powershell 7 version of -replace with a scriptblock 2nd argument. Just assigning $_ into $a to look at it. Note the backquote is a special character inside doublequotes, which I'm avoiding.
'url: `= this.url`' -replace '`= this\.(\w+)`', {$a = $_; '$' + $_.groups[1] + '$'}
url: $url$
$a
Groups : {0, 1}
Success : True
Name : 0
Captures : {0}
Index : 5
Length : 12
Value : `= this.url`
ValueSpan :
tl;dr
# * Consistent use of '...', obviating the need to `-escape ` and $
# * Verbatim $ chars. in the substitution string escaped as $$
# * Capture-group reference $1 represented as ${1} for visual clarity.
(Get-Content .\file) -replace '`= this\.(\w+)`', '$$${1}$$'
Background information and guidance:
In the substitution operand of PowerShell's regex-based -replaceoperator, a verbatim $ character must be escaped as $$, given that $-prefixed tokens have special meaning, namely to refer to results of the regex matching operation, such as $1 in your command (a reference to what the 1st, unnamed capture group in the search regex captured).
Unlike what the docs partially suggest, such a substitution string is not itself a regex, and any other characters are used verbatim.
To programmatically escape $ for verbatim use in a substitution string, it's simplest to use the .Replace() .NET string method, which performs _verbatim (literal) replacements (assuming that all $ instance are to be escaped; e.g. '$foo$'.Replace('$', '$$')
Note that, situationally, a capture-group reference such as $1 may need to be disambiguated as ${1}, and you may always choose to do that for visual clarity, as shown above.
It is only the search operand is a regex, and there all characters that are regex metacharacters must be \-escaped in order to be used verbatim, which can be done:
character-individually, in string literals (amount: \$)
programmatically, for entire strings, using [regex]::Escape() ([regex]::Escape('amount: $'))
To avoid confusion over up-front string interpolation by PowerShell vs. what the .NET regex engine ends up seeing, it's best to consistently use verbatim (single-quoted) strings ('...') rather than expandable (double-quoted) strings ("...").
If embedding PowerShell variable values is needed, use techniques such as:
string concatenation ('^' + [regex]::Escape($foo) + '$')
or -f, the format operator ('^{0}$' -f [regex]::Escape($foo))
In your case, using '...' helps you avoid the `-escaping that "..." requires to make PowerShell treat $ and ` (and ") verbatim, as shown above.
For a comprehensive overview of PowerShell's -replace operator, see this answer.

Matching strings with and without escape characters with RegEx

I have different distinguished names from Active Directory objects and need to filter out escape characters when splitting those dn´s into simple names.
I already have a string -split of PowerShell in place, but this does not filter out escape characters. I´ve tried regex with a positive lookbehind but i do need in this case something like a optional positive lookbehind? Maybe I'm just thinking too complicated.
String examples:
OU=External,OU=T1,OU=\+TE,DC=test,DC=dir
OU=\#External,OU=T1,OU=\+TE,DC=test,DC=dir
OU=\+External,OU=T1,OU=\+TE,DC=test,DC=dir
Because + and # are escaped but are the actual name of those objects, I need to remove the escape characters
With following PowerShell it is possible to get the name of the object
($variable -split ',*..=')[1]
Actual Result:
External
\#External
\+External
Expected Result:
External
#External
+External
It is possible to use regex with $variable -creplace "REGEX" but I cant find a regex which fits all those cases.
My try was: (?<=OU=\\).+?(?=,OU=) but just matches if the \ is there
I need this name for the object creation inside Active Directory.
With minimal change you could just add the slash as optional in your current regex. You already do something similar with the leading comma
"OU=\#External,OU=T1,OU=\+TE,DC=test,DC=dir" -split ',?..=\\?'
You could take that farther if you were just going for the first section but that answers your basic question. There is likely other efficiencies to be made but probably not worth it.
For extracting the first OU name from a DN while removing an optional leading backslash at the same time you can use a regular expression like this:
OU=\\?(.*?), *..=.*$
Demonstration:
$dn1 = 'OU=External,OU=T1,OU=\+TE,DC=test,DC=dir'
$dn2 = 'OU=\#External,OU=T1,OU=\+TE,DC=test,DC=dir'
$dn3 = 'OU=\+External,OU=T1,OU=\+TE,DC=test,DC=dir'
$dn1 -replace 'OU=\\?(.*?), *..=.*$', '$1' # output: External
$dn2 -replace 'OU=\\?(.*?), *..=.*$', '$1' # output: #External
$dn3 -replace 'OU=\\?(.*?), *..=.*$', '$1' # output: +External

Invalid Expression Pattern

The following Regex pattern in PowerShell is giving me real trouble. The double and single quotes are the culprits but I don't know how to get PowerShell to accept it. How do I get PowerShell to successfully accept this pattern?
If I copy the pattern to a variable PowerShell complains about an unexpected token after the first quote found within the pattern.
$myRegex = "^param[\s?]*\([\$\sa-zA-Z\=\#\(\)\"\d\,\:\\\_\.\']*\)"
I then attempted to escape the double quote by adding another quote next to it. This time the string is accepted but the regex fails. Notice the double double quote in the next example.
$myRegex = "^param[\s?]*\([\$\sa-zA-Z\=\#\(\)\""\d\,\:\\\_\.\']*\)"
$somelongString -replace $myRegex
Error Message:
The regular expression pattern ^param[\s?]*\([\$\sa-zA-Z\=\#\(\)\"\d\,\:\\\_\.\']*\) is not valid.
Update 1:
Per #Dan Farrell's suggestion I updated my regex as follows:
$myRegex = "^param(\s?)*\([\$\sa-zA-Z\=\#\(\)\""\d\,\:\\\_\.\']*\)"
Update 2:
This is a working example of my Regex which I am trying to port to PowerShell
Escaping _ in a .NET regex causes an error. To use a " inside "..." string literal, you need to escape it with a backtick, use `". Besides, you only need to escape \ inside your character class.
Use
$myRegex = "^param\s*\([$\sa-zA-Z=#()`"\d,:\\_.']*\)"

How to use a variable as part of a regular expression in PowerShell

I want to Select-String parts of a file path starting at a string value that is contained in a variable. Let me explain this in an abstracted example.
Let's assume this path: /docs/reports/test reports/document1.docx
Using a regular expression I can get the required string like so:
'^.*(?=\/test\s)'
https://regex101.com/r/6mBhLX/5
The resulting string is '/test reports/document1.docx'.
Now, for this to work I have to use the literal string 'test'. However, I would like to know how to use a variable that contains 'test', e.g. $myString.
I already looked at How do you use a variable in a regular expression?, but I couldn't figure out how to adapt this for PowerShell.
I suggest using $([regex]::escape($myString)) inside a double quoted string literal:
$myString="[test]"
$pattern = "^.*(?=/$([regex]::escape($myString))\s)"
Or, in case you do not want to worry with additional escaping, use a regular concatenation using + operator:
$pattern = '^.*(?=/' + [regex]::escape($myString) +'\s)'
The resulting $pattern will look like ^.*(?=/\[test]\s). Since the $myString variable is a literal string, you need to escape all special regex metacharacters (with [regex]::escape()) that may be inside it for the regex engine to interpret it as literal chars.
In your case, you may use
$s = '/docs/reports/test reports/document1.docx'
$myString="test"
$pattern = "^.*(?=/$([regex]::escape($myString))\s)"
$s -replace $pattern
Result: /test reports/document1.docx
Wiktor Stribiżew's helpful answer provides the crucial pointer:
Use [regex]::Escape() in order to escape a string for safe inclusion in a regex (regular expression) so that it is treated as a literal;
e.g., [regex]::Escape('$10?') yields \$10\? - the characters with special meaning to a regex were \-escaped.
However, I suggest using '...', i.e., building the regex from single-quoted aka verbatim strings:
$myString='test'
$regex = '^.*(?=/' + [regex]::escape($myString) + '\s)'
Using the -f operator - $regex = '^.*(?=/{0}'\s)' -f [regex]::Escape($myString) works too and is perhaps visually cleaner, but note that -f - unlike string concatenation with + - is culture-sensitive, which can lead to different results.
Using '...' strings in regex contexts in PowerShell is a good habit to form:
By avoiding "...", so-called expandable strings, you avoid additional up-front interpretation (interpolation a.k.a expansion) of the string, which can have unexpected effects, given that $ has special meaning in both contexts: the start of
a variable reference or subexpression when string-expanding, and the end-of-input marker in regexes.
Using "..." can be especially tricky in the replacement string of the regex-based -replace operator, in whose replacement string operand tokens such as $1 refer to capture-group results, and if you used "$1", PowerShell would try to expand a $1 variable, which presumably doesn't exist, resulting in the empty string.
Just write the variable within double quotes ("pattern"), like this:
PS > $pattern = "^\d+\w+"
PS > "357test*&(fdnsajkfj" -match $pattern # return true
PS > "357test*&(fdnsajkfj" -match "$pattern.*\w+$" # return true
PS > "357test*&(fdnsajkfj" -match "$pattern\w+$" # return false
Please have a try. :)

I want to modify this regex to include apostrophe

This regex is used for validating email addresses, however it doesn't include the case for apostrophy (') which is a valid character in the first part of an email address.
I have tried myself and to use some examples I found, but they don't work.
^([\w-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$
How do I modify it slightly to support the ' character (apostraphy)?
Per the documentation for an email address, the apostrophe can appear anywhere before the # symbol, which, in your current regex is:
^([\w-\.]+)#
You should be able to add the apostrophe into the brackets of valid characters:
^([\w-\.']+)#
This would make the entire regex:
^([\w-\.']+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$
EDIT (regex contained in single-quotes)
If you're using this regex inside a string with single-quotes, such as in PHP with $regex = '^([\w ..., you will need to escape the single-quote in the regex with \':
^([\w-\.\']+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$
You need to update the first part as follows:
^([\'\w-\.]+)