How can I use Regular Expression to convert String to different substring? - regex

Question

I have a text file containing lines, similar to these
000001 , Line 1 of text , customer 1 name
000002 , Line 2 of text , customer 2 name
000003 , Line 3 of text , customer 3 name
= = =
= = =
= = =
000087 , Line 87 of text, customer 87 name
= = =
= = =
001327 , Line 1327 of text, customer 1327 name
= = =
= = =
= = =
I can write a program that reads each line of the above file to convert it to the following format:
000001 , 1st Line , 1st Customer name
000002 , 2nd Line , 2nd Customer name
000003 , 3rd Line , 3rd Customer name
= = =
= = =
= = =
000087 , 87th Line, 87th Customer name
= = =
= = =
001327 , 1327th Line, 1327th Customer name
= = =
= = =
= = =
My Question: is there a straight forward method to achieve the same output using Regular expression?
I tried the following:
Dim pattern As String = "(\d{6}) , (Line \d+ of text) , (customer \d name)"
Dim replacement As String = " $1 , $2 Line , $3 Customer name "
Dim rgx As New Regex(pattern)
Dim result As String = rgx.Replace(my_input_file, replacement)
but the result is far from the desired output.
Please help

Answer 1

Your regex captures too much. The groups should capture only digits:
Dim pattern As String = "(\d{6}) , Line (\d+) of text , customer (\d+) name"
Also, as you want to replace the numbers with ordinal numbers, you should rather use String.Format to do the formatting (line by line):
Dim match as Match = rgx.match(my_input_file_line)
Dim outputLine as String = String.Format(" {0} , {1} Line , {2} Customer name", _
m.Groups(1).Value, GetOrdinal(m.Groups(2).Value), GetOrdinal(m.Groups(3).Value))
where GetOrdinal is a method that changes a string for number to an ordinal number.

Answer 2

Your matching groups are to big. What you want to match are the numbers.
Replace (\d{6}) , Line (\d+) of text , customer (\d+) name
by $1 , $2th Line , $3th Customer name
Then replace 1th by 1st
Then replace 2th by 2nd
Then replace 3th by 3rd
I do not know if it was your intention to match a real cutomer name itself and replace it in another order ... was it?
Then you could use (with global and multiline flags)
^(\d{6}) , Line (\d+) of text , ([^ ]+) (\d) ([^ ]+)$
and replace with $1 , $2th Line , $4th $3 $5
Tip: I allways use http://www.gskinner.com/RegExr/ to test my patterns and experiment with them!

Answer 3

Is there a reason for using regex? Maybe i have misuderstood the requirement, but it seems to be a fix format where only the first part matters, so you could use this simple query:
IEnumerable<string> lines = File.ReadLines(#"folder\input_text.txt");
IEnumerable<string> result = lines
.Where(l => l.Trim().Length > 0)
.Select(l => int.Parse(l.Split(',').First().Trim()))
.Select(num => string.Format("{0} , {1} Line , {1} Customer name"
, num.ToString("D6")
, num + (num == 1 ? "st" : num == 2 ? "nd" : "rd")));
You can use File.WriteAllLines to write the result to the output file:
File.WriteAllLines(#"folder\desired_output.txt", result);