CODEWITHSUNDEEP
c#regex
Wafflze
Wafflze

Reputation: 33

c# regex pattern position and last 3 chars

I am trying to create a new string based on a file name. Part of the name contains irrelevant information like the current year. For example D2015987.txt. For me the important part of the regex is to extract D987 from the part of the file name.

I started off by using Regex.Match(@"D\d{4}|\d{3}\b+"), this seems to trim off the last digit when I get the values. In reality I am attempting to create a new string from this value, so I may also be able to use string newStr = Regex.Replace(pattern).value ...

I also need assistance with creating a new value that will match a pattern similar to this D11Q1987.txt ... from this I need the DQ987 part as well.

Thanks in advance for your help. Dan

Upvotes: 1

Views: 467

Answers (2)

Ahosan Karim Asik
Ahosan Karim Asik

Reputation: 3299

try this : pattern is ^(\w)\d+(\d{3})\.txt$ replace with $1$2

now u use this code in your code according your (C#) syntax. i hope this work. c# code

using System.IO;
using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
    // This is the input string we are replacing parts from.
    string input = "D2015987.txt";

    // Use Regex.Replace to replace the pattern in the input.
    string output = Regex.Replace(input, @"^(\w)\d+(\d{3})\.txt$", "$1$2");

    // Write the output.
    Console.WriteLine(input);
    Console.WriteLine(output);
    }
}

output c#

D2015987.txt
D987

another php solution

$str = "D2015987.txt";

preg_match($re, $str, $matches);
$r=$matches[1].$matches[2];
var_dump($r );

output for php

string 'D987' (length=4)

Upvotes: 1

Regular Jo
Regular Jo

Reputation: 5510

  1. (.) grabs the first, capture group 1
  2. \d+ matches any number of digits (but at least one)
  3. ([A-Za-z]) matches a single character, and captures it as group 1.
  4. \d matches a single digit.
  5. (\d{3}) matches three digits.
  6. \. escapes the period.
  7. txt finishes it off looking for the literal characters txt

Regex:

    (.)\d+([A-Za-z])\d(\d{3})\.txt

Now, if the last digits are variable length, but always preceded by a digit, we simply change the {3} to +. 

    (.)\d+([A-Za-z])\d(\d+)\.txt

$1 contains D (by your example), `$2' contains Q (by your example) and $3 contains 987, but both examples depend on being preceded by a digit that we can use as a marker but throw away.

Upvotes: 0

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