PowerShell Regex - word with wildcards and commas - regex

Question

Trying to do a replace on what I understand to be a simple operation but hitting a wall.
I can replace a word with a comma on the end:
$firstval = 'ssonp,RDPNP,LanmanWorkstation,webclient,MfeEpePcNP,PRNetworkProvider'
($firstval) -replace 'webclient+,',''
ssonp,RDPNP,LanmanWorkstation,MfeEpePcNP,PRNetworkProvider
But haven't been able to work out how to add a wildcard in the word, or how I'd have multiple words with wildcards proceeded by a comma, e.g.:
w* client+,* fee*, etc
(spaces added to stop being interpreted as formatting within the question)
Played with a few permeations and attempted to use examples from other questions without any luck.

Answer 1

The -replace operator takes a regular expression as its first parameter. You seem to be confusing wildcards and regular expressions. Your pattern w*client+,*fee*,, though a valid regular expression, seems to be intended to use wildcards.
The regular expression equivalent of the * wildcard is .*, where . means "any character" and * means "0 or more occurrences". Thus, the regular expression equivalent of w*client, would be w.*client,, and, similarly the regular expression equivalent of *fee*, would be .*fee.*,. Since the string to be searched has comma-separated values, however, we don't want our patterns to include "any character" (.*) but rather "any character but comma" ([^,]*). Therefore, the patterns to use become w[^,]*client, and [^,]*fee[^,]*,, respectively.
To search for both words in a string, separate the two patterns with |. The following builds such a pattern and tests it against strings with a match in various locations:
# Match w*client or *fee*
$wordPattern = 'w[^,]*client|[^,]*fee[^,]*';
# Match $wordPattern and at most one comma before or after
$wordWithAdjacentCommaPattern = '({0}),?|,({0})$' -f $wordPattern;
"`$wordWithAdjacentCommaPattern: $wordWithAdjacentCommaPattern";
# Replace single value
'webclient', `
# Replace first value
'webclient,middle,last', `
# Replace middle value
'first,webclient,last', `
# Replace last value
'first,middle,webclient' `
| ForEach-Object -Process { '"{0}" => "{1}"' -f $_, ($_ -replace $wordWithAdjacentCommaPattern); };
This outputs the following:
$wordWithAdjacentCommaPattern: (w[^,]*client|[^,]*fee[^,]*),?|,(w[^,]*client|[^,]*fee[^,]*)$
"webclient" => ""
"webclient,middle,last" => "middle,last"
"first,webclient,last" => "first,last"
"first,middle,webclient" => "first,middle"
A non-regex alternative you might consider would be to split your input string into individual values, filter out values that match certain wildcards, and reassemble what's left into comma-separated values:
(
'ssonp,RDPNP,LanmanWorkstation,webclient,MfeEpePcNP,PRNetworkProvider' -split ',', -1, 'SimpleMatch' `
| Where-Object { $_ -notlike 'w*client' -and $_ -notlike '*fee*'; } `
) -join ',';
By the way, you used the regular expression webclient+, to match and remove the text webclient, from your string (looks like the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\NetworkProvider\Order\ProviderOrder registry value). Just a note that, with the +, that will search for the literal text webclien followed by 1 or more occurrences of t followed by the literal text ,. Thus, that will match webclientt,, webclienttt,, webclientttttttttt,, etc. as well webclient,. If you are only interested in matching webclient, then you can just use the pattern webclient, (no +).