正则表达式提取字符串中每四个逗号的匹配项

Question

I am trying to create a regex to get a output for below string, in sets of 4 comma separated values. I have tried something but it only selects each comma separated value. I don't know how to get the desired output.

The regex I tried:

".*?"(?=,|$)

Data:

"T","Success","2","2","T","Success","6458960","1","F,"You do not have sufficient credit.","6458962","1"

Desired out:

"T","Success","2","2"  
"T","Success","6458960","1"  
"F,"You do not have sufficient credit.","6458962","1"

Update: "The F is in double quote too, it was a typo, Sorry!"

"T","Success","2","2","T","Success","6458960","1","F","You do not have sufficient credit.","6458962","1"

Answer 1

You just need String.Split and this:

string[] fields = str.Split(',');
for (int i = 0; i < fields.Length; i += 4)
    Console.WriteLine(string.Join(",", fields.Skip(i).Take(4)));

Output:

"T","Success","2","2"
"T","Success","6458960","1"
"F,"You do not have sufficient credit.","6458962","1"

This presumes that this is not really csv data. Otherwise i would suggest to use a real CSV parser that supports quoting characters . But it seems that they are broken anyway( ,"1","F,. , so F is not enclosed in quotes).

Answer 2

You could use following regex, but only if the F is also in enclosed quotes:

((?:".+",){3}(?:".+"))

This results in:

MATCH 1 1. [0-21] "T","Success","2","2"

MATCH 2 1. [22-49] "T","Success","6458960","1"

MATCH 3 1. [50-104] "F","You do not have sufficient credit.","6458962","1"

Regex Demo

If the data is really in this inconsistent form, you have to parse it manually or modify the regex with an or condition.

Answer 3

((?:"[^"]*"|[^,"])*(?:,(?:"[^"]*"|[^,"])*){3}),?

1. (?:"[^"]*"|[^,"])* will match a values between commas, optionally quoted. Quotes are escaped as "" .

2. (X(?:,X){3}),? where X is pattern #1, will match a sequence of four comma-separated values, and an optional trailing comma. The comma is necessary to correctly match blank values ( ,,foo, ).

If the values are guaranteed to always have quotes, you can remove |[^,"] and ,? .

Answer 4

You can try this regex,but the regex has a problem:you need to trim then last Comma ,and even there are much more Comma in string, not multiple of 4 Comma ,it can also works fine

string patten = @"(?<=^(?:(?:[^,]*,){4})+)";
string text = @"""T"",""Success"",""2"",""2"",""T"",""Success"",""6458960"",""1"",""F,""You do not have sufficient credit."",""6458962"",""1""";
foreach (var tmp in Regex.Split(text, patten))
{
    Console.WriteLine(tmp.TrimEnd(','));
}

Answer 5

I would avoid regex unless you really need it, generally they can be harder to understand.

For fun here is a Linq solution:

var data = @"""T"",""Success"",""2"",""2"",""T"",""Success"",""6458960"",""1"",""F,""You do not have sufficient credit."",""6458962"",""1""";

var res = data.Split(',')
            .Select((x ,i) => new { Pos = i / 4, Val = x })
            .GroupBy(x => x.Pos)
            .Select(g => string.Join(",", g.Select(x => x.Val)));