Problem
I am working on a script that has a user provide a specific IP address and I want to mask this IP in some fashion so that it isn't stored in the logs. My problem is, that I can easily do this when I know what the first three values of the IP typically are; however, I want to avoid storing/hard coding those values into the code to if at all possible. I also want to be able to replace the values even if the first three are unknown to me.
Examples:
10.11.12.50 would display as XX.XX.XX.50
10.12.11.23 would also display as XX.XX.XX.23
I have looked up partial string replacements, but none of the questions or problems that I found came close to doing this. I have tried doing things like:
# This ended up replacing all of the numbers
$tempString = $str -replace '[0-9]', 'X'
I know that I am partway there, but I aiming to only replace only the first 3 sets of digits so, basically every digit that is before a '.', but I haven't been able to achieve this.
Question
Is what I'm trying to do possible to achieve with PowerShell? Is there a best practice way of achieving this?
Here's an example of how you can accomplish this:
Get-Content 'File.txt' |
ForEach-Object { $_ = $_ -replace '\d{1,3}\.\d{1,3}\.\d{1,3}','xx.xx.xx' }
This example matches a digit 1-3 times, a literal period, and continues that pattern so it'll capture anything from 0-999.0-999.0-999 and replace with xx.xx.xx
TheIncorrigible1's helpful answer is an exact way of solving the problem (replacement only happens if 3 consecutive .-separated groups of 1-3 digits are matched.)
A looser, but shorter solution that replaces everything but the last .-prefixed digit group:
PS> '10.11.12.50' -replace '.+(?=\.\d+$)', 'XX.XX.XX'
XX.XX.XX.50
(?=\.\d+$) is a (positive) lookahead assertion ((?=...)) that matches the enclosed subexpression (a literal . followed by 1 or more digits (\d) at the end of the string ($)), but doesn't capture it as part of the overall match.
The net effect is that only what .+ captured - everything before the lookahead assertion's match - is replaced with 'XX.XX.XX'.
Applied to the above example input string, 10.11.12.50:
(?=\.\d+$) matches the .-prefixed digit group at the end, .50.
.+ matches everything before .50, which is 10.11.12.
Since the (?=...) part isn't captured, it is therefore not included in what is replaced, so it is only substring 10.11.12 that is replaced, namely with XX.XX.XX, yielding XX.XX.XX.50 as a result.
Related
I'm looking for a regsub example that does the following:
123tcl456TCL789 => 123!tcl!456!TCL!789
This is an Tcl example => This is an !Tcl! example
Yes, I could use string first to find a position and mash things but I saw in past a regsub command that does what I want but I can't recall. What would be the regsub command that allows that? I would guess regsub -all -nocase is a start.
I am bad at regsub and regexps. I wonder if there is a site or tool/script that we can supply a string, the final result and then we get the regsub form.
You're looking at the right tool, but there are various options, depending on exactly what the conditions are when faced with other text. Here's one that wraps each occurrence of "Tcl" (any capitalisation) with exclamation marks:
set inputString "123tcl456TCL789"
set replaced [regsub -all -nocase {tcl} $inputString {!&!}]
puts $replaced
That's using a very simple regular expression with the -nocase option, and the replacement means "put ! on either side of the substring matched".
Another (more generally applicable... perhaps) might be to put ! after any letter or number sequence that is followed by a number or letter.
set replaced [regsub -all {[A-Za-z]+(?=[0-9])|[0-9]+(?=[A-Za-z])} $inputString {&!}]
Note that doing things correctly typically requires understanding the real input data fairly well. For example, whether the numbers include floating point numbers in scientific notation, or whether the substrings to delimit are of fixed length.
I am trying to write a Powershell code to identify a string with a specific character from a filename from multiple files.
An example of a filename
20190902091031_202401192_50760_54206_6401.pdf
$Variable = $Filename.Substring(15,9)
Results:
202401192 (this is what I am after)
However in some instances the filename will be like below
20190902091031_20240119_50760_54206_6401.pdf
$Variable = $Filename.Substring(15,9)
Results:
20240119_ (this is NOT what I am after)
I am trying to find a code to identify the 9th character,
IF the 9th character = "_"
THEN Set
$Variable = $Filename.Substring(15,8)
Results:
20240119
All credit to TheMadTechnician who beat me to the punch with this answer.
To expand on the technique a bit, use the split method or operator to split a string every time a certain character shows up. Your data is separated by the underscore character, so is a perfect example of using this technique. By using either of the following:
$FileName.Split('_')
$FileName -split '_'
You can turn your long string into an array of shorter strings, each containing one of the parts of your original string. Since you want the 2nd one, you use the array descriptor [1] (0 is 1st) and you're done.
Good luck
I am trying to create a regular expression to determine if a string contains a number for an SQL statement. If the value is numeric, then I want to add 1 to it. If the number is not numeric, I want to return a 1. More or less. Here is the SQL:
SELECT
field,
CASE
WHEN regexp_like(field, '^ *\d*\.?\d* *$') THEN dec(field) + 1
ELSE 1
END nextnumber
FROM mytable
This actually works, and returns something like this:
INVALID 1
00000 1
00001E 1
00379 380
00013 14
99904 99905
But to push the envelope of understanding, what if I wanted to cover negative numbers, or those with a positive sign. The sign would have to immediately precede or follow the number, but not both, and I would not want to allow white space between the sign and the number.
I came up with a conditional expression with a capture group to capture the sign on the front of the number to determine if a sign was allowed on the end, but it seems a little awkward to handle given I don't really need a yes-pattern.
Here is the modified regex: ^ ([+-]?)*\d*\.?\d*(?(1) *|[+-]? *)$
This works at regex101.com, but in order for it to work I need to have something before the pipe, so I have to duplicate the next pattern in both the yes-pattern and the no-pattern.
All that background for this question: How can I avoid that duplication?
EDIT: DB2 for i uses International Components for Unicode to provide regular expression processing. It turns out that this library does not support conditionals like PRCE, so I changed the tags on this question. The answer given by Wiktor Stribiżew provides a working alternative to the conditional by using a negative lookahead.
You do not have to duplicate the end pattern, just move it outside the conditional:
^ *([+-])?\d*\.?\d*(?(1)|[+-]?) *$
See the regex demo. So, the yes-part is empty, and the no-part has an optional pattern.
You may also solve it with a mere negative lookahead:
^ *([+-](?!.*[-+]))?\d*\.?\d*[+-]? *$
See another regex demo. Here, ([+-](?!.*[-+]))? matches (optionally) a + or - that are not followed with any 0+ char followed with another + or -.
I've got a bunch of directory names and file names, some are absolute path, some are relative path. I just wish to get the 2 leading parts of each path. Input:
D:\a\b\c\d.txt\
c:\a
\my\desk\n.txt
you\their\mine
I expect to get:
D:\a
c:\a
\my\desk
you\their
Is there a convenient way in PowerShell to achieve this?
You can sometimes get your hand slapped for suggesting string manipulation as it can sometimes be "unreliable". However your test data contains 3 different possibilities. Also, never seen someone looking for the first parts from a path.
I present a simple solution the nets your desired output as you have it in your question
"D:\a\b\c\d.txt\","c:\a","\my\desk\n.txt","you\their\mine" | ForEach-Object{
($_ -split "(?<=\S)\\")[0..1] -join "\"
}
I needed to use a lookbehind since your sample output contains a leading a leading slash that you wanted to retain. It splits every string on slashes that have a non white-space character in front of them.
This would not return the correct path for UNC's. Split-Path would be the obvious choice if you only wanted a single portion of the path. I suppose you could nest the call to get 2 but at this time I am unable to find a simple way to account for all of your examples with the same logic.
How to use matlab regexprep , for multiple expression and replacements?
file='http:xxx/sys/tags/Rel/total';
I want to replace 'sys' with sys1 and 'total' with 'total1'. For a single expression a replacement it works like this:
strrep(file,'sys', 'sys1')
and want to have like
strrep(file,'sys','sys1','total','total1') .
I know this doesn't work for strrep
Why not just issue the command twice?
file = 'http:xxx/sys/tags/Rel/total';
file = strrep(file,'sys','sys1')
strrep(file,'total','total1')
To solve it you need substitute functionality with regex, try to find in matlab's regexes something similar to this in php:
$string = 'http:xxx/sys/tags/Rel/total';
preg_replace('/http:(.*?)\//', 'http:${1}1/', $string);
${1} means 1st match group, that is what in parenthesis, (.*?).
http:(.*?)\/ - match pattern
http:${1}1/ - replace pattern with second 1 as you wish to add (first 1 is a group number)
http:xxx/sys/tags/Rel/total - input string
The secret is that whatever is matched by (.*?) (whether xxx or yyyy or 1234) will be inserted instead of ${1} in replace pattern, and then replace instead of old stuff into the input string. Welcome to see more examples on substitute functionality in php.
As documented in the help page for regexprep, you can specify pairs of patterns and replacements like this:
file='http:xxx/sys/tags/Rel/total';
regexprep(file, {'sys' 'total'}, {'sys1' 'total1'})
ans =
http:xxx/sys1/tags/Rel/total1
It is even possible to use tokens, should you be able to define a match pattern for everything you want to replace:
regexprep(file, '/([st][yo][^/$]*)', '/$11')
ans =
http:xxx/sys1/tags/Rel/total1
However, care must be taken with the first approach under certain circumstances, because MATLAB replaces the pairs one after another. That is to say if, say, the first pattern matches a string and replaces it with something that is subsequently matched by a later pattern, then that will also be replaced by the later replacement, even though it might not have matched the later pattern in the original string.
Example:
regexprep('This\is{not}LaTeX.', {'\\' '([{}])'}, {'\\textbackslash{}' '\\$1'})
ans =
This\textbackslash\{\}is\{not\}LaTeX.
=> This\{}is{not}LaTeX.
and
regexprep('This\is{not}LaTeX.', {'([{}])' '\\'}, {'\\$1' '\\textbackslash{}'})
ans =
This\textbackslash{}is\textbackslash{}{not\textbackslash{}}LaTeX.
=> This\is\not\LaTeX.
Both results are unintended, and there seems to be no way around this with consecutive replacements instead of simultaneous ones.