Replace first and last character to Upper case in PowerShell

Question

Replace first and last character to Upper case in PowerShell

Blue412 21

Can we change the first and last characters to uppercase? Something like the below output? TitleCase works to change the first character to uppercase, was stuck on the last character. Any help is appreciated :)

Input: Servername01

Desired Output: ServernamE01

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Answer 1

I really wish Microsoft actually supported the PCRE regex code. Sadly, it does not.

Your request (pretty easily handled in other languages) could be done like this:

$s -replace '^([a-z])(.+)([a-z])(\d\d)$', '\U$1\E$2\U$3\E$4'

Where "/U" says to convert characters that follow to uppercase, and "/E" says to cease the conversion.

Unfortunately, you'll have to resort to other means to accomplish this:

$s -match '^([a-z])(.+)([a-z])(\d\d)$'
$u = "{0}{1}{2}{3}" -f $matches[1].ToUpper(), $matches[2], $matches[3].ToUpper(), $matches[4]

It does the same thing, but the replacement happens outside the regex. :-(

Answer 2

Blue412 21

@Rich Matheisen Yeah, agree on that point, but the mentioned approach defeats the purpose when we have a undefined character count in the server name and can't specify the exact match count.

I tried trimming the last char in the string and writing the output to two variables. Then capturing the last char with substring and length approach to new variable and then making it uppercase and finally joining them

$input = 'servername'
$pattern = (get-culture).textinfo
$result = $pattern.totitlecase($input.ToLower())
$rest_char = $result.Substring(0,$result.Length-1)
$final_char = ($result.Substring($result.Length-1)).toupper()
$final_result = $rest_char+$final_char

Might be a dumb approach, but got the job done. Just looking for some pointers, if i can do this better way?

Thanks :)

Rich Matheisen 47,901 Reputation points

2021-12-21T15:26:58.07+00:00

Is there a pattern to your server names? The regex I used doesn't depend on the number of characters, provided the entire string is at least five characters long (any shorter and the match will fail).

If the pattern "ccccccccdd" (where "c" is a non-digit, and "d" is a digit) isn't what you use then would it be safe to say that regardless of the last two characters in the string you want to turn the 3rd-from-last character into an uppercase version of itself? Does it matter if that character isn't in the range "A" - "Z"?
DaveK 1,871 Reputation points

2021-12-21T16:09:40.707+00:00
I've been watching this one as I don't have a lot of regex experience so always keen to pickup tips.

This worked for me but only for servers with 2 digits at the end and in my case we sometime have servers which are 1 or 2 digits. I changed the regex to

^([a-z])(.+)([a-z])(\d+)$'

and it now looks to match any length string with any number of digits, as long as its 5 length or more.

DaveK 1,871

I used this to test it

    $Servers = @("onedigitserver1","twodigitserver02", "threedigitserver123","sma11")
    $Servers | Foreach {
        write-host "--------"
        write-host $_
        $_ -match '^([a-z])(.+)([a-z])(\d+)$'
        $u = "{0}{1}{2}{3}" -f $matches[1].ToUpper(), $matches[2].ToLower(), $matches[3].ToUpper(), $matches[4]
        $u
    }

Rich Matheisen 47,901 Reputation points

2021-12-21T19:59:50.44+00:00

Probably more than you want to know, but it's worth reading (just not all at once!).

"Mastering Regular Expressions" by Jeffrey Friedl (ISBN-13: 978-0596528126)

A problem with that regex is that it will match ANY number of digits. If the strings are only supposed to end with one or two digits then last group should probably be "(\d\d?)" meaning "one, and maybe two, digits". Or "(\d{1,2})", but then you make the regex engine keep count. That's not a problem here, but it can be a problem with very long matches because it slows things down. If you have millions of strings to match you want to be as specific as possible with the way you tell the engine to do the matching.

Answer 3

Blue412 21

@DaveK and @Rich Matheisen thanks for the input. We only have either a single or double digit in the end of servername and this one addressed it.

$s -match '^([a-z])(.+)([a-z])(\d+)$'
$u = "{0}{1}{2}{3}" -f $matches[1].ToUpper(), $matches[2], $matches[3].ToUpper(), $matches[4].ToUpper()

Thanks.

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Replace first and last character to Upper case in PowerShell

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