Related
Slightly similar to this question, I want to replace argv contents:
string argv = "-help=none\n-URL=(default)\n-password=look\n-uname=Khanna\n-p=100";
to this:
"-help=none\n-URL=(default)\n-password=********\n-uname=Khanna\n-p=100"
I have tried very basic string find and search operations (using IndexOf, SubString etc.). I am looking for more elegant solution so as to replace this part of string:
-password=AnyPassword
to:
-password=*******
And keep other part of string intact. I am looking if String.Replace or Regex replace may help.
What I've tried (not much of error-checks):
var pwd_index = argv.IndexOf("--password=");
string converted;
if (pwd_index >= 0)
{
var leftPart = argv.Substring(0, pwd_index);
var pwdStr = argv.Substring(pwd_index);
var rightPart = pwdStr.Substring(pwdStr.IndexOf("\n") + 1);
converted = leftPart + "--password=********\n" + rightPart;
}
else
converted = argv;
Console.WriteLine(converted);
Solution
Similar to Rubens Farias' solution but a little bit more elegant:
string argv = "-help=none\n-URL=(default)\n-password=\n-uname=Khanna\n-p=100";
string result = Regex.Replace(argv, #"(password=)[^\n]*", "$1********");
It matches password= literally, stores it in capture group $1 and the keeps matching until a \n is reached.
This yields a constant number of *'s, though. But telling how much characters a password has, might already convey too much information to hackers, anyway.
Working example: https://dotnetfiddle.net/xOFCyG
Regular expression breakdown
( // Store the following match in capture group $1.
password= // Match "password=" literally.
)
[ // Match one from a set of characters.
^ // Negate a set of characters (i.e., match anything not
// contained in the following set).
\n // The character set: consists only of the new line character.
]
* // Match the previously matched character 0 to n times.
This code replaces the password value by several "*" characters:
string argv = "-help=none\n-URL=(default)\n-password=look\n-uname=Khanna\n-p=100";
string result = Regex.Replace(argv, #"(password=)([\s\S]*?\n)",
match => match.Groups[1].Value + new String('*', match.Groups[2].Value.Length - 1) + "\n");
You can also remove the new String() part and replace it by a string constant
I have no experience using regular expressions, and although I should spend some time training in them, I have a need for a simple one.
I want to find a match of P*.txt in a given string (meaning anything that starts with a P, followed by anything, and ending in ".txt".
eg:
string myString = "P671221.txt";
Regex reg = new Regex("P*.txt"); //<--- what goes here?
if (reg.IsMatch(myString)
{
Console.WriteLine("Match!"));
}
This example doesn't work because it will return a match for ".txt" or "x.txt" etc. How do I do this?
myString.StartsWith("P") && myString.EndsWith(".txt")
EDIT: Removed my regex
Updated:
string start + (p) + any characters + .txt + string end
^(?i:p).*\.txt$
A more precise alternative would be:
string start + (p) + [specific characters] + .txt + string end
( currently specified are: "a-z", "0-9", space, & underscore )
^(?i:p)(?i:[a-z0-9 _])*\.txt$
Live Demo
Original Solution
( quotes were included, as I overlooked that quotes are part of the code but not
the string )
preceding quotes + (p) + any characters + .txt + following quotes
(?<=")(?i:p).*\.txt(?=")
Image
Live Demo
P[\d]+\.txt this will work. If you have fix number of digits then you can do it like P[\d]{6}\.txt. Just replace the 6 with your desired fix number.
If the value in between the starting letter P and extension .txt can be alphanumeric use P[\w]+\.txt
string myString = "P671221.txt";
Regex reg = new Regex("P(.*?)\\.txt"); //--> if anything goes after P
if (reg.IsMatch(myString))
Console.WriteLine("Match!");
This should meet the requirements that you have presented.
c#
[Pp].*.(?:txt)+$
The best option to get files that start with P & end with .txt with regex is:
^P\w+\.txt$
Having a bit of a problem as I have to translate a string into a table. I'd like to remove multiple spaces, but not all of them. So the data in text comes back with lots of spaces in between like so:
SESSIONNAME USERNAME ID STATE TYPE DEVICE\r\n
services 0 Disc \r\n
console 1 Conn \r\n
alinav 2 Disc \r\n
rdp-tcp 65536 Listen \r\n
I would like to still keep the \r\n\ values that will define my rows, and I want to keep the empty value which would be legit under the columns, and I want to keep the spaces to define the columns. But I want to remove the extra spaces that I don't want to be fed into the values.
I've tried:
output = Regex.Replace(output, #"\s{2,}", " ", RegexOptions.Multiline);
output = output.Replace(" ", " ");
But the first one just removes everything (things I need and don't need). And the second one still leaves too many spaces.
Thanks.
You can do two things:
Use space explicitly in the regular expression, \s includes weird characters like (\n, \r, \t,...) as well, thus:
output = Regex.Replace(output, #" +", " ", RegexOptions.Multiline);
Or apply the second method until convergence:
string s2 = output;
do {
output = s2;
s2 = s2.Replace(" "," ");
} while(output != s2);
In most cases the first method will outperform the second one. This because the first method groups all substrings with two or more spaces. Regexes are in general a bit slower than simple string replacement, but if the string contains sequences with many spaces, the first method will be faster.
In your example the data is delimited by position, not by characters; is that correct? If so, you should extract by position; something like:
foreach (string s in output.Split())
{
var sessionName = s.Substring(0, 18).Trim();
var userName = s.Substring(18, 19).Trim();
var id = Int32.Parse(s.Substring(37, 8).Trim());
var whateverType = s.Substring(45, 12).Trim();
var device = s.Substring(57, 6).Trim();
}
Of course you need to do proper error checking, and should probably put the field widths in an array and calculate positions instead of hard-coding them as I have shown.
How can I replace Line Breaks within a string in C#?
Use replace with Environment.NewLine
myString = myString.Replace(System.Environment.NewLine, "replacement text"); //add a line terminating ;
As mentioned in other posts, if the string comes from another environment (OS) then you'd need to replace that particular environments implementation of new line control characters.
The solutions posted so far either only replace Environment.NewLine or they fail if the replacement string contains line breaks because they call string.Replace multiple times.
Here's a solution that uses a regular expression to make all three replacements in just one pass over the string. This means that the replacement string can safely contain line breaks.
string result = Regex.Replace(input, #"\r\n?|\n", replacementString);
To extend The.Anyi.9's answer, you should also be aware of the different types of line break in general use. Dependent on where your file originated, you may want to look at making sure you catch all the alternatives...
string replaceWith = "";
string removedBreaks = Line.Replace("\r\n", replaceWith).Replace("\n", replaceWith).Replace("\r", replaceWith);
should get you going...
I would use Environment.Newline when I wanted to insert a newline for a string, but not to remove all newlines from a string.
Depending on your platform you can have different types of newlines, but even inside the same platform often different types of newlines are used. In particular when dealing with file formats and protocols.
string ReplaceNewlines(string blockOfText, string replaceWith)
{
return blockOfText.Replace("\r\n", replaceWith).Replace("\n", replaceWith).Replace("\r", replaceWith);
}
If your code is supposed to run in different environments, I would consider using the Environment.NewLine constant, since it is specifically the newline used in the specific environment.
line = line.Replace(Environment.NewLine, "newLineReplacement");
However, if you get the text from a file originating on another system, this might not be the correct answer, and you should replace with whatever newline constant is used on the other system. It will typically be \n or \r\n.
if you want to "clean" the new lines, flamebaud comment using regex #"[\r\n]+" is the best choice.
using System;
using System.Text.RegularExpressions;
class MainClass {
public static void Main (string[] args) {
string str = "AAA\r\nBBB\r\n\r\n\r\nCCC\r\r\rDDD\n\n\nEEE";
Console.WriteLine (str.Replace(System.Environment.NewLine, "-"));
/* Result:
AAA
-BBB
-
-
-CCC
DDD---EEE
*/
Console.WriteLine (Regex.Replace(str, #"\r\n?|\n", "-"));
// Result:
// AAA-BBB---CCC---DDD---EEE
Console.WriteLine (Regex.Replace(str, #"[\r\n]+", "-"));
// Result:
// AAA-BBB-CCC-DDD-EEE
}
}
Use new in .NET 6 method
myString = myString.ReplaceLineEndings();
Replaces ALL newline sequences in the current string.
Documentation:
ReplaceLineEndings
Don't forget that replace doesn't do the replacement in the string, but returns a new string with the characters replaced. The following will remove line breaks (not replace them). I'd use #Brian R. Bondy's method if replacing them with something else, perhaps wrapped as an extension method. Remember to check for null values first before calling Replace or the extension methods provided.
string line = ...
line = line.Replace( "\r", "").Replace( "\n", "" );
As extension methods:
public static class StringExtensions
{
public static string RemoveLineBreaks( this string lines )
{
return lines.Replace( "\r", "").Replace( "\n", "" );
}
public static string ReplaceLineBreaks( this string lines, string replacement )
{
return lines.Replace( "\r\n", replacement )
.Replace( "\r", replacement )
.Replace( "\n", replacement );
}
}
To make sure all possible ways of line breaks (Windows, Mac and Unix) are replaced you should use:
string.Replace("\r\n", "\n").Replace('\r', '\n').Replace('\n', 'replacement');
and in this order, to not to make extra line breaks, when you find some combination of line ending chars.
Why not both?
string ReplacementString = "";
Regex.Replace(strin.Replace(System.Environment.NewLine, ReplacementString), #"(\r\n?|\n)", ReplacementString);
Note: Replace strin with the name of your input string.
I needed to replace the \r\n with an actual carriage return and line feed and replace \t with an actual tab. So I came up with the following:
public string Transform(string data)
{
string result = data;
char cr = (char)13;
char lf = (char)10;
char tab = (char)9;
result = result.Replace("\\r", cr.ToString());
result = result.Replace("\\n", lf.ToString());
result = result.Replace("\\t", tab.ToString());
return result;
}
var answer = Regex.Replace(value, "(\n|\r)+", replacementString);
As new line can be delimited by \n, \r and \r\n, first we’ll replace \r and \r\n with \n, and only then split data string.
The following lines should go to the parseCSV method:
function parseCSV(data) {
//alert(data);
//replace UNIX new lines
data = data.replace(/\r\n/g, "\n");
//replace MAC new lines
data = data.replace(/\r/g, "\n");
//split into rows
var rows = data.split("\n");
}
Use the .Replace() method
Line.Replace("\n", "whatever you want to replace with");
Best way to replace linebreaks safely is
yourString.Replace("\r\n","\n") //handling windows linebreaks
.Replace("\r","\n") //handling mac linebreaks
that should produce a string with only \n (eg linefeed) as linebreaks.
this code is usefull to fix mixed linebreaks too.
Another option is to create a StringReader over the string in question. On the reader, do .ReadLine() in a loop. Then you have the lines separated, no matter what (consistent or inconsistent) separators they had. With that, you can proceed as you wish; one possibility is to use a StringBuilder and call .AppendLine on it.
The advantage is, you let the framework decide what constitutes a "line break".
string s = Regex.Replace(source_string, "\n", "\r\n");
or
string s = Regex.Replace(source_string, "\r\n", "\n");
depending on which way you want to go.
Hopes it helps.
If you want to replace only the newlines:
var input = #"sdfhlu \r\n sdkuidfs\r\ndfgdgfd";
var match = #"[\\ ]+";
var replaceWith = " ";
Console.WriteLine("input: " + input);
var x = Regex.Replace(input.Replace(#"\n", replaceWith).Replace(#"\r", replaceWith), match, replaceWith);
Console.WriteLine("output: " + x);
If you want to replace newlines, tabs and white spaces:
var input = #"sdfhlusdkuidfs\r\ndfgdgfd";
var match = #"[\\s]+";
var replaceWith = "";
Console.WriteLine("input: " + input);
var x = Regex.Replace(input, match, replaceWith);
Console.WriteLine("output: " + x);
This is a very long winded one-liner solution but it is the only one that I had found to work if you cannot use the the special character escapes like "\r" and "\n" and \x0d and \u000D as well as System.Environment.NewLine as parameters to thereplace() method
MyStr.replace( System.String.Concat( System.Char.ConvertFromUtf32(13).ToString(), System.Char.ConvertFromUtf32(10).ToString() ), ReplacementString );
This is somewhat offtopic but to get it to work inside Visual Studio's XML .props files, which invoke .NET via the XML properties, I had to dress it up like it is shown below.
The Visual Studio XML --> .NET environment just would not accept the special character escapes like "\r" and "\n" and \x0d and \u000D as well as System.Environment.NewLine as parameters to thereplace() method.
$([System.IO.File]::ReadAllText('MyFile.txt').replace( $([System.String]::Concat($([System.Char]::ConvertFromUtf32(13).ToString()),$([System.Char]::ConvertFromUtf32(10).ToString()))),$([System.String]::Concat('^',$([System.Char]::ConvertFromUtf32(13).ToString()),$([System.Char]::ConvertFromUtf32(10).ToString())))))
Based on #mark-bayers answer and for cleaner output:
string result = Regex.Replace(ex.Message, #"(\r\n?|\r?\n)+", "replacement text");
It removes \r\n , \n and \r while perefer longer one and simplify multiple occurances to one.
Doing a search for different strings using wildcards, such as doing a search for test0? (there is a space after the ?). The strings the search produces are:
test01
test02
test03
(and so on)
The replacement text should be for example:
test0? -
The wildcard above in test0? - represents the 1, 2, or 3...
So, the replacement strings should be:
test01 -
test02 -
test03 -
string pattern = WildcardToRegex(originalText);
fileName = Regex.Replace(originalText, pattern, replacementText);
public string WildcardToRegex(string pattern)
{
return "^" + System.Text.RegularExpressions.Regex.Escape(pattern).
Replace("\\*", ".*").Replace("\\?", ".") + "$";
}
The problem is saving the new string with the original character(s) plus the added characters. I could search the string and save the original with some string manipulation, but that seems like too much overhead. There has to be an easier way.
Thanks for any input.
EDIT:
Search for strings using the wildcard ?
Possible string are:
test01 someText
test02 someotherText
test03 moreText
Using Regex, the search string patter will be:
test0? -
So, each string should then read:
test01 - someText
test02 - someotherText
test03 - moreText
How to keep the character that was replaced by the regex wildcard '?'
As my code stands, it will come out as test? - someText
That is wrong.
Thanks.
EDIT Num 2
First, thanks everyone for their answers and direction.
It did help and lead me to the right track and now I can better ask the exact question:
It has to do with substitution.
Inserting text after the Regex.
The sample string I gave, they may not always be in that format. I have been looking into substitution but just can't seem to get the syntax right. And I am using VS 2008.
Any more suggestions?
Thanks
If you want to replace "test0? " with "test0? -", you would write:
string bar = Regex.Replace(foo, "^test0. ", "$0- ");
The key here is the $0 substitution, which will include the matched text.
So if I understand your question correctly, you just want your replacementText to be "$0- ".
If I understand the question correctly, couldn't you just use a match?
//Convert pattern to regex (I'm assuming this can be done with your "originalText")
Regex regex = pattern;
//For each match, replace the found pattern with the original value + " -"
foreach (Match m in regex.Matches)
{
RegEx.Replace(pattern, m.Groups[0].Value + " -");
}
So I'm not 100% clear on what you're doing, but I'll give it a try.
I'm going with the assumption that you want to use "file wildcards" (?/*) and search for a set of values that match (while retaining the values stored using the placeholder itself), then replace it with the new value (re-inserting those placeholders). given that, and probably a lot of overkill (since your requirement is kind of weird) here's what I came up with:
// Helper function to turn the file search pattern in to a
// regex pattern.
private Regex BuildRegexFromPattern(String input)
{
String pattern = String.Concat(input.ToCharArray().Select(i => {
String c = i.ToString();
return c == "?" ? "(.)"
: c == "*" ? "(.*)"
: c == " " ? "\\s"
: Regex.Escape(c);
}));
return new Regex(pattern);
}
// perform the actual replacement
private IEnumerable<String> ReplaceUsingPattern(IEnumerable<String> items, String searchPattern, String replacementPattern)
{
Regex searchRe = BuildRegexFromPattern(searchPattern);
return items.Where(s => searchRe.IsMatch(s)).Select (s => {
Match match = searchRe.Match(s);
Int32 m = 1;
return String.Concat(replacementPattern.ToCharArray().Select(i => {
String c = i.ToString();
if (m > match.Groups.Count)
{
throw new InvalidOperationException("Replacement placeholders exceeds locator placeholders.");
}
return c == "?" ? match.Groups[m++].Value
: c == "*" ? match.Groups[m++].Value
: c;
}));
});
}
Then, in practice:
String[] samples = new String[]{
"foo01", "foo02 ", "foo 03",
"bar0?", "bar0? ", "bar03 -",
"test01 ", "test02 ", "test03 "
};
String searchTemplate = "test0? ";
String replaceTemplate = "test0? -";
var results = ReplaceUsingPattern(samples, searchTemplate, replaceTemplate);
Which, from the samples list above, gives me:
matched: & modified to:
test01 test01 -
test02 test02 -
test03 test03 -
However, if you really want to save headaches you should be using replacement references. there's no need to re-invent the wheel. The above, with replacements, could have been changed to:
Regex searchRe = new Regex("test0(.*)\s");
samples.Select(x => searchRe.Replace(s, "test0$1-"));
You can catch any piece of your matched string and place anywhere in the replace statement, using symbol $ followed by the index of catched element (it starts at index 1).
You can catch element with parenthesis "()"
Example:
If I have several strings with testXYZ, being XYZ a 3-digit number, and I need to replace it, say, with testZYX, inverting the 3 digits, I would do:
string result = Regex.Replace(source, "test([0-9])([0-9])([0-9])", "test$3$2$1");
So, in your case, it can be done:
string result = Regex.Replace(source, "test0([0-9]) ", "test0$1 - ");