I am looking Regex formula for Dart, to check either the input is matching specific any string or not which I proved. Example: input is 'butter', and proved strings are ['but','burst','bus']. The program should return false because 'but' is not equal to the 'butter'. But it is returning true as below code.
void main() {
const string = 'Can you give me a butter';
const pattern = r'(but)|(burst)|(bus)';
final regExp = RegExp(pattern);
print(regExp.hasMatch(string.toLowerCase())); //true
}
When I changed the codes as below it worked well.
void main() {
const string = 'Can you give me a But asasa';
const pattern = r'\b(but|burst|bus)\b';
final regExp = RegExp(pattern, caseSensitive: false);
print(regExp.hasMatch(string));
}
For matching a whole word, the regex \bword\b should suffice. Yet the following code always returns 0 matches
try {
string pattern = "\bhtml\b";
Regex wordRegex = new Regex (pattern, RegexCompileFlags.CASELESS, RegexMatchFlags.NOTEMPTY);
MatchInfo matchInfo;
string lineOfText = "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">";
wordRegex.match (lineOfText, RegexMatchFlags.NOTEMPTY, out matchInfo);
stdout.printf ("Match count is: %d\n", matchInfo.get_match_count ());
} catch (RegexError regexError) {
stderr.printf ("Regex error: %s\n", regexError.message);
}
This should be working as testing the \bhtml\b pattern returns one match for the provided string in testing engines. But on this program it returns 0 matches. Is the code wrong? What regex in Glib would be used to match a whole word?
It looks like you have to escape the backslash too:
try {
string pattern = "\\bhtml\\b";
Regex wordRegex = new Regex (pattern, RegexCompileFlags.CASELESS, RegexMatchFlags.NOTEMPTY);
MatchInfo matchInfo;
string lineOfText = "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">";
wordRegex.match (lineOfText, RegexMatchFlags.NOTEMPTY, out matchInfo);
stdout.printf ("Match count is: %d\n", matchInfo.get_match_count ());
} catch (RegexError regexError) {
stderr.printf ("Regex error: %s\n", regexError.message);
}
Output:
Match count is: 1
Demo
You can simplify your code with regular expression literals:
Regex regex = /\bhtml\b/i;
You don't have to quote backslashes in the regular expression literal syntax. (Front slashes would be problematic though.)
Full example:
void test_match (string text, Regex regex) {
MatchInfo match_info;
if (regex.match (text, RegexMatchFlags.NOTEMPTY, out match_info)) {
stdout.printf ("Match count is: %d\n", match_info.get_match_count ());
}
else {
stdout.printf ("No match");
}
}
int main () {
Regex regex = /\bhtml\b/i;
test_match ("<!DOCTYPE html PUBLIC>", regex);
return 0;
}
static String AdrPattern="http://www.([^&]+)\\.com\\.*";
static Pattern WebUrlPattern = Pattern.compile (AdrPattern);
static Matcher WebUrlMatcher;
WebUrlMatcher = WebUrlPattern.matcher ("keyword");
if(WebUrlMatcher.matches())
String extractedPath = WebUrlMatcher.group (1);
Considering above codes, My aim is to extract the domain name from the URL and dismiss the rest. But the trouble is that, first of all, if the URL has deeper path, it will not ignore it and second, it does not work for all URL with .com extension.
For example, if the URL is http://www.lego.com/en-us/technic/?domainredir=technic.lego, the result will not be lego but lego.com/en-us/technic/?domainredir=technic.lego.
Use
static String AdrPattern="http://www\\.([^&]+)\\.com.*";
^^ ^
You escaped the final dot, and it was treated as a literal, and matches could not match the entire string. Also, the first dot must be escaped.
Also, to make the regex a bit more strict, you can replace the [^&]+ with [^/&].
UPDATE:
static String AdrPattern="http://www\\.([^/&]+)\\.com/([^/]+)/([^/]+)/([^/]+).*";
static Pattern WebUrlPattern = Pattern.compile (AdrPattern);
static Matcher WebUrlMatcher = WebUrlPattern.matcher("http://www.lego.com/en-us/technic/?domainredir=technic.lego");
if(WebUrlMatcher.matches()) {
String extractedPath = WebUrlMatcher.group(1);
String extractedPart1 = WebUrlMatcher.group(2);
String extractedPart2 = WebUrlMatcher.group(3);
String extractedPart3 = WebUrlMatcher.group(4);
}
Or, with \G:
static String AdrPattern="(?:http://www\\.([^/&]+)\\.com/|(?!^)\\G)/?([^/]+)";
static String AdrPattern="http://www\\.([^/&]+)\\.com/([^/]+)/([^/]+)/([^/]+)";
static Pattern WebUrlPattern = Pattern.compile (AdrPattern);
static Matcher WebUrlMatcher = WebUrlPattern.matcher("http://www.lego.com/en-us/technic/?domainredir=technic.lego");
int cnt = 0;
while(WebUrlMatcher.find()) {
if (cnt == 0) {
String extractedPath = WebUrlMatcher.group(1);
String extractedPart = WebUrlMatcher.group(2);
cnt = cnt + 1;
}
else {
String extractedPart = WebUrlMatcher.group(2);
}
}
Could someone explain why this snip :
// import com.google.gwt.regexp.shared.MatchResult;
// import com.google.gwt.regexp.shared.RegExp;
RegExp regExp = RegExp.compile("^$");
MatchResult matcher;
while ((matcher = regExp.exec("")) != null)
{
System.out.println("match " + matcher);
}
give an incredible count of matches? I tested with different modifier allowed by GWT implementation of compile(), g, i and m. It works only with m (multiline).
I just want to check for empty string.
[EDIT] the new method
private ArrayList<MatchResult> getMatches(String input, String pattern)
{
ArrayList<MatchResult> matches = new ArrayList<MatchResult>();
if(null == regExp)
{
regExp = RegExp.compile(pattern, "g");
}
if(input.isEmpty())
{
// empty string : just check if pattern validate and
// don't try to extract matches : it will resutl in infinite
// loop.
if(regExp.test(input))
{
matches.add(new MatchResult(0, "", new ArrayList<String>(0)));
}
}
else
{
for(MatchResult matcher = regExp.exec(input); matcher != null; matcher = regExp
.exec(input))
{
matches.add(matcher);
}
}
return matches;
}
Your regExp.exec("") with RegExp.compile("^$") will never return null, as the empty string "" is a match for regex ^$, which reads "nothing between beginning and the end of line/string".
So your while is infinity loop.
Also, you print is
System.out.println("match " + matcher);
...but you probably wanted to use
System.out.println("match " + matcher.getGroup(0));
Also see GWT checking if textbox is empty.
I've got a wildcard pattern, perhaps "*.txt" or "POS??.dat".
I also have list of filenames in memory that I need to compare to that pattern.
How would I do that, keeping in mind I need exactly the same semantics that IO.DirectoryInfo.GetFiles(pattern) uses.
EDIT: Blindly translating this into a regex will NOT work.
I have a complete answer in code for you that's 95% like FindFiles(string).
The 5% that isn't there is the short names/long names behavior in the second note on the MSDN documentation for this function.
If you would still like to get that behavior, you'll have to complete a computation of the short name of each string you have in the input array, and then add the long name to the collection of matches if either the long or short name matches the pattern.
Here is the code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
namespace FindFilesRegEx
{
class Program
{
static void Main(string[] args)
{
string[] names = { "hello.t", "HelLo.tx", "HeLLo.txt", "HeLLo.txtsjfhs", "HeLLo.tx.sdj", "hAlLo20984.txt" };
string[] matches;
matches = FindFilesEmulator("hello.tx", names);
matches = FindFilesEmulator("H*o*.???", names);
matches = FindFilesEmulator("hello.txt", names);
matches = FindFilesEmulator("lskfjd30", names);
}
public string[] FindFilesEmulator(string pattern, string[] names)
{
List<string> matches = new List<string>();
Regex regex = FindFilesPatternToRegex.Convert(pattern);
foreach (string s in names)
{
if (regex.IsMatch(s))
{
matches.Add(s);
}
}
return matches.ToArray();
}
internal static class FindFilesPatternToRegex
{
private static Regex HasQuestionMarkRegEx = new Regex(#"\?", RegexOptions.Compiled);
private static Regex IllegalCharactersRegex = new Regex("[" + #"\/:<>|" + "\"]", RegexOptions.Compiled);
private static Regex CatchExtentionRegex = new Regex(#"^\s*.+\.([^\.]+)\s*$", RegexOptions.Compiled);
private static string NonDotCharacters = #"[^.]*";
public static Regex Convert(string pattern)
{
if (pattern == null)
{
throw new ArgumentNullException();
}
pattern = pattern.Trim();
if (pattern.Length == 0)
{
throw new ArgumentException("Pattern is empty.");
}
if(IllegalCharactersRegex.IsMatch(pattern))
{
throw new ArgumentException("Pattern contains illegal characters.");
}
bool hasExtension = CatchExtentionRegex.IsMatch(pattern);
bool matchExact = false;
if (HasQuestionMarkRegEx.IsMatch(pattern))
{
matchExact = true;
}
else if(hasExtension)
{
matchExact = CatchExtentionRegex.Match(pattern).Groups[1].Length != 3;
}
string regexString = Regex.Escape(pattern);
regexString = "^" + Regex.Replace(regexString, #"\\\*", ".*");
regexString = Regex.Replace(regexString, #"\\\?", ".");
if(!matchExact && hasExtension)
{
regexString += NonDotCharacters;
}
regexString += "$";
Regex regex = new Regex(regexString, RegexOptions.Compiled | RegexOptions.IgnoreCase);
return regex;
}
}
}
}
You can simply do this. You do not need regular expressions.
using Microsoft.VisualBasic.CompilerServices;
if (Operators.LikeString("pos123.txt", "pos?23.*", CompareMethod.Text))
{
Console.WriteLine("Filename matches pattern");
}
Or, in VB.Net,
If "pos123.txt" Like "pos?23.*" Then
Console.WriteLine("Filename matches pattern")
End If
In c# you could simulate this with an extension method. It wouldn't be exactly like VB Like, but it would be like...very cool.
You could translate the wildcards into a regular expression:
*.txt -> ^.+\.txt$
POS??.dat _> ^POS..\.dat$
Use the Regex.Escape method to escape the characters that are not wildcars into literal strings for the pattern (e.g. converting ".txt" to "\.txt").
The wildcard * translates into .+, and ? translates into .
Put ^ at the beginning of the pattern to match the beginning of the string, and $ at the end to match the end of the string.
Now you can use the Regex.IsMatch method to check if a file name matches the pattern.
Just call the Windows API function PathMatchSpecExW().
[Flags]
public enum MatchPatternFlags : uint
{
Normal = 0x00000000, // PMSF_NORMAL
Multiple = 0x00000001, // PMSF_MULTIPLE
DontStripSpaces = 0x00010000 // PMSF_DONT_STRIP_SPACES
}
class FileName
{
[DllImport("Shlwapi.dll", SetLastError = false)]
static extern int PathMatchSpecExW([MarshalAs(UnmanagedType.LPWStr)] string file,
[MarshalAs(UnmanagedType.LPWStr)] string spec,
MatchPatternFlags flags);
/*******************************************************************************
* Function: MatchPattern
*
* Description: Matches a file name against one or more file name patterns.
*
* Arguments: file - File name to check
* spec - Name pattern(s) to search foe
* flags - Flags to modify search condition (MatchPatternFlags)
*
* Return value: Returns true if name matches the pattern.
*******************************************************************************/
public static bool MatchPattern(string file, string spec, MatchPatternFlags flags)
{
if (String.IsNullOrEmpty(file))
return false;
if (String.IsNullOrEmpty(spec))
return true;
int result = PathMatchSpecExW(file, spec, flags);
return (result == 0);
}
}
Some kind of regex/glob is the way to go, but there are some subtleties; your question indicates you want identical semantics to IO.DirectoryInfo.GetFiles. That could be a challenge, because of the special cases involving 8.3 vs. long file names and the like. The whole story is on MSDN.
If you don't need an exact behavioral match, there are a couple of good SO questions:
glob pattern matching in .NET
How to implement glob in C#
For anyone who comes across this question now that it is years later, I found over at the MSDN social boards that the GetFiles() method will accept * and ? wildcard characters in the searchPattern parameter. (At least in .Net 3.5, 4.0, and 4.5)
Directory.GetFiles(string path, string searchPattern)
http://msdn.microsoft.com/en-us/library/wz42302f.aspx
Plz try the below code.
static void Main(string[] args)
{
string _wildCardPattern = "*.txt";
List<string> _fileNames = new List<string>();
_fileNames.Add("text_file.txt");
_fileNames.Add("csv_file.csv");
Console.WriteLine("\nFilenames that matches [{0}] pattern are : ", _wildCardPattern);
foreach (string _fileName in _fileNames)
{
CustomWildCardPattern _patetrn = new CustomWildCardPattern(_wildCardPattern);
if (_patetrn.IsMatch(_fileName))
{
Console.WriteLine("{0}", _fileName);
}
}
}
public class CustomWildCardPattern : Regex
{
public CustomWildCardPattern(string wildCardPattern)
: base(WildcardPatternToRegex(wildCardPattern))
{
}
public CustomWildCardPattern(string wildcardPattern, RegexOptions regexOptions)
: base(WildcardPatternToRegex(wildcardPattern), regexOptions)
{
}
private static string WildcardPatternToRegex(string wildcardPattern)
{
string patternWithWildcards = "^" + Regex.Escape(wildcardPattern).Replace("\\*", ".*");
patternWithWildcards = patternWithWildcards.Replace("\\?", ".") + "$";
return patternWithWildcards;
}
}
For searching against a specific pattern, it might be worth using File Globbing which allows you to use search patterns like you would in a .gitignore file.
See here: https://learn.microsoft.com/en-us/dotnet/core/extensions/file-globbing
This allows you to add both inclusions & exclusions to your search.
Please see below the example code snippet from the Microsoft Source above:
Matcher matcher = new Matcher();
matcher.AddIncludePatterns(new[] { "*.txt" });
IEnumerable<string> matchingFiles = matcher.GetResultsInFullPath(filepath);
The use of RegexOptions.IgnoreCase will fix it.
public class WildcardPattern : Regex {
public WildcardPattern(string wildCardPattern)
: base(ConvertPatternToRegex(wildCardPattern), RegexOptions.IgnoreCase) {
}
public WildcardPattern(string wildcardPattern, RegexOptions regexOptions)
: base(ConvertPatternToRegex(wildcardPattern), regexOptions) {
}
private static string ConvertPatternToRegex(string wildcardPattern) {
string patternWithWildcards = Regex.Escape(wildcardPattern).Replace("\\*", ".*");
patternWithWildcards = string.Concat("^", patternWithWildcards.Replace("\\?", "."), "$");
return patternWithWildcards;
}
}