I am having trouble with string replacement in powershell. Please consider the following expression:
"replaceTarget: %rep" -replace '%rep','$_'
I expect the result of this expression to be:
replaceTarget: $_
but instead, it is
replaceTarget: replaceTarget: $rep
I assume it is because the replacement string '$_' has some other meaning in the replace function.
How can I escape the input string so that $_ can be passed in without being evaluated?
try with this:
'replaceTarget: %rep' -replace '%rep','$$_'
you coud use the .net replace function like this :
'replaceTarget: $rep'.replace("`$rep",'$_')
Related
Been scratching my head on this one...
I'd like to remove .com and capitalize S and T from: "sometext.com"
So output would be Some Text
Thank you in advance
For most of this you can use the replace() member of the String object.
The syntax is:
$string = $string.replace('what you want replaced', 'what you will replace it with')
Replace can be used to erase things by using blank quotes '' for the second argument. That's how you can get rid of .com
$string = $string.replace('.com','')
It can also be used to insert things. You can insert a space between some and text like this:
$string = $string.replace('et', 'e t')
Note that using replace does NOT change the original variable. The command below will print "that" to your screen, but the value of $string will still be "this"
$string = 'this'
$string.replace('this', 'that')
You have to set the variable to the new value with =
$string = "this"
$string = $string.replace("this", "that")
This command will change the value of $string to that.
The tricky part here comes in changing the first t to capital T without changing the last t. With strings, replace() replaces every instance of the text.
$string = "text"
$string = $string.replace('t', 'T')
This will set $string to TexT. To get around this, you can use Regex. Regex is a complex topic. Here just know that Regex objects look like strings, but their replace method works a little differently. You can add a number as a third argument to specify how many items to replace
$string = "aaaaaa"
[Regex]$reggie = 'a'
$string = $reggie.replace($string,'a',3)
This code sets $string to AAAaaa.
So here's the final code to change sometext.com to Some Text.
$string = 'sometext.com'
#Use replace() to remove text.
$string = $string.Replace('.com','')
#Use replace() to change text
$string = $string.Replace('s','S')
#Use replace() to insert text.
$string = $string.Replace('et', 'e t')
#Use a Regex object to replace the first instance of a string.
[regex]$pattern = 't'
$string = $pattern.Replace($string, 'T', 1)
What you're trying to achieve isn't well-defined, but here's a concise PowerShell Core solution:
PsCore> 'sometext.com' -replace '\.com$' -replace '^s|t(?!$)', { $_.Value.ToUpper() }
SomeText
-replace '\.com$' removes a literal trailing .com from your input string.
-replace '^s|t(?!$), { ... } matches an s char. at the start (^), and a t that is not (!) at the end ($); (?!...) is a so-called negative look-ahead assertion that looks ahead in the input string without including what it finds in the overall match.
Script block { $_.Value.ToUpper() } is called for each match, and converts the match to uppercase.
-replace (a.k.a -ireplace) is case-INsensitive by default; use -creplace for case-SENSITIVE replacements.
For more information about PowerShell's -replace operator see this answer.
Passing a script block ({ ... }) to dynamically determine the replacement string isn't supported in Windows PowerShell, so a Windows PowerShell solution requires direct use of the .NET [regex] class:
WinPs> [regex]::Replace('sometext.com' -replace '\.com$', '^s|t(?!$)', { param($m) $m.Value.ToUpper() })
SomeText
I have a list of users in a text file who's names are in the following format: xn-tsai-01.
How do I script to remove the xn- KEEP THIS -01 so the output is like: tsai
I know how to do this in bash but not too familiar with powershell.
Thanks in advance!
Why not use Substring method. If you will always trim the first three characters, you can do the following assuming the variable is a string type.
$string = xn-tsai-01
$string.Substring(3)
Here is a quick way to do it using regex:
'xn-tsai-01' -replace '.*?-(.*)-.*','$1'
Example with a list:
(Get-Content list.txt) -Replace '.*?-(.*)-.*','$1'
You can use the .NET string method IndexOf("-") to find the first, and LastIndexOf("-") to find the last occurrence of "-" within the string.
Use these indexes with Substring() to remove the unnecessary parts:
function Clean-Username {
param($Name)
$FirstDash = $Name.IndexOf("-") + 1
$LastDash = $Name.LastIndexOf("-")
return $Name.Substring( $f, $l - $f )
}
PS C:\> Clean-UserName -Name "xn-tsai-01"
tsai
Boe's example is probably going to be the most efficient.
Another way is to use the split() method if they're in a uniform format.
Get-Content .\list.txt | % { ($_.Split('-'))[1] }
% is an alias for ForEach
I have a method that has an if statement that catches if it finds a special character. What I want to do now if find the position of the special characters and replace it with _A
Some Examples
test# becomes test_A
I#hope#someone#knows#the#answer# becomes I_Ahope_Asomeone_Aknows_Athe_Aanswer_A
or if it has more than one special character
You?didnt#understand{my?Question# becomes You_Adidnt_Aunderstand_Amy_AQuestion_A
Would I have to loop through the whole string and when I reach that character change it to _A or is there a quicker way of doing this?
# is just a character like any other, you can use the -replace operator:
PS C:\>'I#hope#someone#knows#the#answer#' -replace '#','_A'
I_Ahope_Asomeone_Aknows_Athe_Aanswer_A
Regex is magic, you can define all the special cases you like (braces will have to be escaped):
PS C:\>'You?didnt#understand{my?Question#' -replace '[#?\{]','_A'
You_Adidnt_Aunderstand_Amy_AQuestion_A
So your function could look something like this:
function Replace-SpecialChars {
param($InputString)
$SpecialChars = '[#?\{\[\(\)\]\}]'
$Replacement = '_A'
$InputString -replace $SpecialChars,$Replacement
}
Replace-SpecialChars -InputString 'You?didnt#write{a]very[good?Question#'
If you are unsure of which characters to escape, have the regex class do it for you!
function Replace-SpecialChars {
param(
[string]$InputString,
[string]$Replacement = "_A",
[string]$SpecialChars = "#?()[]{}"
)
$rePattern = ($SpecialChars.ToCharArray() |ForEach-Object { [regex]::Escape($_) }) -join "|"
$InputString -replace $rePattern,$Replacement
}
Alternatively, you can use the .NET string method Replace():
'You?didnt#understand{my?Question#'.Replace('#','_A').Replace('?','_A').Replace('{','_A')
But I feel the regex way is more concise
In Powershell given the following string
$string = "this is a sample of 'my' text $PSP.what do you think"
how do I use the -replace function to convert the string to
this is a sample of 'my' text Hello.what do you think
I obviously need to escape the string somehow, Also $PSP is not a declared variable in my script
I need to change all mentions of $PSP for some other string
Use the backtick character (above the tab key):
$string = "this is a sample of 'my' text `$PSP.what do you think"
To replace the dollar sign using the -replace operator, escape it with backslash:
"this is a sample of 'my' text `$PSP.what do you think" -replace '\$PSP', 'hello'
Or use the string.replace method:
$string = "this is a sample of 'my' text `$PSP.what do you think"
$string.Replace('$PSP','Hello)'
this is a sample of 'my' text Hello.what do you think
Unless you modify your original string (e.g. by escaping the $), this is isn't (really) possible.
Your $string doesn't really contain a $PSP, as it is replaced by nothing in the assignment statement.
$string = "this is a sample of 'my' text $PSP.what do you think"
$string -eq "this is a sample of 'my' text .what do you think"
evaluates to:
True
This comes up as the first answer in google even though it is really old, so I will add my slight variation.
In my case I was reading in a file and replacing a string with $s in it.
The short version of my file is:
<version>$version$<version>
In the case where one is actiong on a (file) stream, variables are not autoreplaced so there is no need to escape the $ in the file.
In the replacement pattern you can avoid the interpretation of the variable using ' instead of ".
My final command looked like:
(gc $fileName) | % { $_.replace('$version$', "$BuildNumber") } | sc $fileName
This is a file read(get-content) piped through the replace and back in to the file with a set-content.
You should try
$string = $string.Replace("\$PSP", "Hello")
or
$string = $string.Replace("\$PSP", $the_new_value)
or to be more generic use Regex
$string = [regex]::Replace($string, "\$\w+", "Hello")
I am trying to implement macro replacement based on this discussion. Basically it works, but seems the ExpandString have some limitatoins:
main.ps1:
$foo = 'foo'
$text = [IO.File]::ReadAllText('in.config')
$ExecutionContext.InvokeCommand.ExpandString($text) | out-file 'out.config'
in.config (OK):
$foo
in.config (Error: "Encountered end of line while processing a string token."):
"
in.config (Error: "Missing ' at end of string."):
'
The documentation states:
Return Value: The expanded string
with all the variable and expression
substitutions done.
What is 'expression substitution' (may be this is my case)?
Is there some workaround?
The error is occurring because quotes (single and double) are special characters to the PowerShell runtime. They indicate a string and if they are to be used as just that character, they need to be escaped.
A possible workaround would be to escape quotes with a backtick, depending on your desired result.
For example if my text file had
'$foo'
The resulting expansion of that string would be
PS>$text = [io.file]::ReadAllText('test.config')
PS>$ExecutionContext.InvokeCommand.ExpandString($text)
$foo
If you wanted to have that variable expanded, you would need to escape those quotes.
`'$foo`'
PS>$text = [io.file]::ReadAllText('test.config')
PS>$ExecutionContext.InvokeCommand.ExpandString($text)
'foo'
or if you were going to have an unpaired single or double quote, you would need to escape it.
You could do a -replace on the string to escape those characters, but you'll have to make sure that is the desired effect across the board.
PS>$single, $double = "'", '"'
PS>$text = [io.file]::ReadAllText('test.config') -replace "($single|$double)", '`$1'
PS>$ExecutionContext.InvokeCommand.ExpandString($text)
NOTE: After you do the ExpandString call, you won't have the backticks hanging around anymore.