I have the following comma-separated string that I need to split. The problem is that some of the content is within quotes and contains commas that shouldn't be used in the split.
String:
111,222,"33,44,55",666,"77,88","99"
I want the output:
111
222
33,44,55
666
77,88
99
I have tried this:
(?:,?)((?<=")[^"]+(?=")|[^",]+)
But it reads the comma between "77,88","99" as a hit and I get the following output:
111
222
33,44,55
666
77,88
,
99
Depending on your needs you may not be able to use a csv parser, and may in fact want to re-invent the wheel!!
You can do so with some simple regex
(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)
This will do the following:
(?:^|,) = Match expression "Beginning of line or string ,"
(\"(?:[^\"]+|\"\")*\"|[^,]*) = A numbered capture group, this will select between 2 alternatives:
This should give you the output you are looking for.
Example code in C#
static Regex csvSplit = new Regex("(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)", RegexOptions.Compiled);
public static string[] SplitCSV(string input)
{
List<string> list = new List<string>();
string curr = null;
foreach (Match match in csvSplit.Matches(input))
{
curr = match.Value;
if (0 == curr.Length)
{
list.Add("");
}
list.Add(curr.TrimStart(','));
}
return list.ToArray();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
Console.WriteLine(SplitCSV("111,222,\"33,44,55\",666,\"77,88\",\"99\""));
}
Warning As per @MrE's comment - if a rogue new line character appears in a badly formed csv file and you end up with an uneven ("string) you'll get catastrophic backtracking (https://www.regular-expressions.info/catastrophic.html) in your regex and your system will likely crash (like our production system did). Can easily be replicated in Visual Studio and as I've discovered will crash it. A simple try/catch will not trap this issue either.
You should use:
(?:^|,)(\"(?:[^\"])*\"|[^,]*)
instead
Fast and easy:
public static string[] SplitCsv(string line)
{
List<string> result = new List<string>();
StringBuilder currentStr = new StringBuilder("");
bool inQuotes = false;
for (int i = 0; i < line.Length; i++) // For each character
{
if (line[i] == '\"') // Quotes are closing or opening
inQuotes = !inQuotes;
else if (line[i] == ',') // Comma
{
if (!inQuotes) // If not in quotes, end of current string, add it to result
{
result.Add(currentStr.ToString());
currentStr.Clear();
}
else
currentStr.Append(line[i]); // If in quotes, just add it
}
else // Add any other character to current string
currentStr.Append(line[i]);
}
result.Add(currentStr.ToString());
return result.ToArray(); // Return array of all strings
}
With this string as input :
111,222,"33,44,55",666,"77,88","99"
It will return :
111
222
33,44,55
666
77,88
99
i really like jimplode's answer, but I think a version with yield return is a little bit more useful, so here it is:
public IEnumerable<string> SplitCSV(string input)
{
Regex csvSplit = new Regex("(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)", RegexOptions.Compiled);
foreach (Match match in csvSplit.Matches(input))
{
yield return match.Value.TrimStart(',');
}
}
Maybe it's even more useful to have it like an extension method:
public static class StringHelper
{
public static IEnumerable<string> SplitCSV(this string input)
{
Regex csvSplit = new Regex("(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)", RegexOptions.Compiled);
foreach (Match match in csvSplit.Matches(input))
{
yield return match.Value.TrimStart(',');
}
}
}
This regular expression works without the need to loop through values and TrimStart(','), like in the accepted answer:
((?<=\")[^\"]*(?=\"(,|$)+)|(?<=,|^)[^,\"]*(?=,|$))
Here is the implementation in C#:
string values = "111,222,\"33,44,55\",666,\"77,88\",\"99\"";
MatchCollection matches = new Regex("((?<=\")[^\"]*(?=\"(,|$)+)|(?<=,|^)[^,\"]*(?=,|$))").Matches(values);
foreach (var match in matches)
{
Console.WriteLine(match);
}
Outputs
111
222
33,44,55
666
77,88
99
None of these answers work when the string has a comma inside quotes, as in "value, 1", or escaped double-quotes, as in "value ""1""", which are valid CSV that should be parsed as value, 1 and value "1", respectively.
This will also work with the tab-delimited format if you pass in a tab instead of a comma as your delimiter.
public static IEnumerable<string> SplitRow(string row, char delimiter = ',')
{
var currentString = new StringBuilder();
var inQuotes = false;
var quoteIsEscaped = false; //Store when a quote has been escaped.
row = string.Format("{0}{1}", row, delimiter); //We add new cells at the delimiter, so append one for the parser.
foreach (var character in row.Select((val, index) => new {val, index}))
{
if (character.val == delimiter) //We hit a delimiter character...
{
if (!inQuotes) //Are we inside quotes? If not, we've hit the end of a cell value.
{
Console.WriteLine(currentString);
yield return currentString.ToString();
currentString.Clear();
}
else
{
currentString.Append(character.val);
}
} else {
if (character.val != ' ')
{
if(character.val == '"') //If we've hit a quote character...
{
if(character.val == '\"' && inQuotes) //Does it appear to be a closing quote?
{
if (row[character.index + 1] == character.val) //If the character afterwards is also a quote, this is to escape that (not a closing quote).
{
quoteIsEscaped = true; //Flag that we are escaped for the next character. Don't add the escaping quote.
}
else if (quoteIsEscaped)
{
quoteIsEscaped = false; //This is an escaped quote. Add it and revert quoteIsEscaped to false.
currentString.Append(character.val);
}
else
{
inQuotes = false;
}
}
else
{
if (!inQuotes)
{
inQuotes = true;
}
else
{
currentString.Append(character.val); //...It's a quote inside a quote.
}
}
}
else
{
currentString.Append(character.val);
}
}
else
{
if (!string.IsNullOrWhiteSpace(currentString.ToString())) //Append only if not new cell
{
currentString.Append(character.val);
}
}
}
}
}
With minor updates to the function provided by "Chad Hedgcock".
Updates are on:
Line 26: character.val == '\"' - This can never be true due to the check made on Line 24. i.e. character.val == '"'
Line 28: if (row[character.index + 1] == character.val) added !quoteIsEscaped to escape 3 consecutive quotes.
public static IEnumerable<string> SplitRow(string row, char delimiter = ',')
{
var currentString = new StringBuilder();
var inQuotes = false;
var quoteIsEscaped = false; //Store when a quote has been escaped.
row = string.Format("{0}{1}", row, delimiter); //We add new cells at the delimiter, so append one for the parser.
foreach (var character in row.Select((val, index) => new {val, index}))
{
if (character.val == delimiter) //We hit a delimiter character...
{
if (!inQuotes) //Are we inside quotes? If not, we've hit the end of a cell value.
{
//Console.WriteLine(currentString);
yield return currentString.ToString();
currentString.Clear();
}
else
{
currentString.Append(character.val);
}
} else {
if (character.val != ' ')
{
if(character.val == '"') //If we've hit a quote character...
{
if(character.val == '"' && inQuotes) //Does it appear to be a closing quote?
{
if (row[character.index + 1] == character.val && !quoteIsEscaped) //If the character afterwards is also a quote, this is to escape that (not a closing quote).
{
quoteIsEscaped = true; //Flag that we are escaped for the next character. Don't add the escaping quote.
}
else if (quoteIsEscaped)
{
quoteIsEscaped = false; //This is an escaped quote. Add it and revert quoteIsEscaped to false.
currentString.Append(character.val);
}
else
{
inQuotes = false;
}
}
else
{
if (!inQuotes)
{
inQuotes = true;
}
else
{
currentString.Append(character.val); //...It's a quote inside a quote.
}
}
}
else
{
currentString.Append(character.val);
}
}
else
{
if (!string.IsNullOrWhiteSpace(currentString.ToString())) //Append only if not new cell
{
currentString.Append(character.val);
}
}
}
}
}
For Jay's answer, if you use a 2nd boolean then you can have nested double-quotes inside single-quotes and vice-versa.
private string[] splitString(string stringToSplit)
{
char[] characters = stringToSplit.ToCharArray();
List<string> returnValueList = new List<string>();
string tempString = "";
bool blockUntilEndQuote = false;
bool blockUntilEndQuote2 = false;
int characterCount = 0;
foreach (char character in characters)
{
characterCount = characterCount + 1;
if (character == '"' && !blockUntilEndQuote2)
{
if (blockUntilEndQuote == false)
{
blockUntilEndQuote = true;
}
else if (blockUntilEndQuote == true)
{
blockUntilEndQuote = false;
}
}
if (character == '\'' && !blockUntilEndQuote)
{
if (blockUntilEndQuote2 == false)
{
blockUntilEndQuote2 = true;
}
else if (blockUntilEndQuote2 == true)
{
blockUntilEndQuote2 = false;
}
}
if (character != ',')
{
tempString = tempString + character;
}
else if (character == ',' && (blockUntilEndQuote == true || blockUntilEndQuote2 == true))
{
tempString = tempString + character;
}
else
{
returnValueList.Add(tempString);
tempString = "";
}
if (characterCount == characters.Length)
{
returnValueList.Add(tempString);
tempString = "";
}
}
string[] returnValue = returnValueList.ToArray();
return returnValue;
}
Currently I use the following regex:
public static Regex regexCSVSplit = new Regex(@"(?x:(
(?<FULL>
(^|[,;\t\r\n])\s*
( (?<QUODAT> (?<QUO>[""'])(?<DAT>([^,;\t\r\n]|(?<!\k<QUO>\s*)[,;\t\r\n])*)\k<QUO>) |
(?<QUODAT> (?<DAT> [^""',;\s\r\n]* )) )
(?=\s*([,;\t\r\n]|$))
) |
(?<FULL>
(^|[\s\t\r\n])
( (?<QUODAT> (?<QUO>[""'])(?<DAT> [^""',;\s\t\r\n]* )\k<QUO>) |
(?<QUODAT> (?<DAT> [^""',;\s\t\r\n]* )) )
(?=[,;\s\t\r\n]|$)
)
))", RegexOptions.Compiled);
This solution can handle pretty chaotic cases too like below:
This is how to feed the result into an array:
var data = regexCSVSplit.Matches(line_to_process).Cast<Match>().
Select(x => x.Groups["DAT"].Value).ToArray();
See this example in action HERE
Note: The regular expression contains two set of <FULL> block and each of them contains two <QUODAT> block separated by "or" (|). Depending on your task you may only need one of them.
Note: That this regular expression gives us one string array, and works on single line with or without <carrier return> and/or <line feed>.
The following regular expression will already cover many complex cases:
public static Regex regexCSVSplit = new Regex(@"(?x:(
(?<FULL>
(^|[,;\t\r\n])\s*
(?<QUODAT> (?<QUO>[""'])(?<DAT>([^,;\t\r\n]|(?<!\k<QUO>\s*)[,;\t\r\n])*)\k<QUO>)
(?=\s*([,;\t\r\n]|$))
)
))", RegexOptions.Compiled);
See this example in action: HERE
It can process complex, easy and empty items too:
This is how to feed the result into an array:
var data = regexCSVSplit.Matches(line_to_process).Cast<Match>().
Select(x => x.Groups["DAT"].Value).ToArray();
The main rule here is that every item may contain anything but the <quotation mark><separators><comma> sequence AND each item shall being and end with the same <quotation mark>.
<quotation mark>: <">, <'><comma>: <,>, <;>, <tab>, <carrier return>, <line feed>Edit notes: I added some more explanation to make it easier to understand and replaces the text "CO" with "QUO".
I know I'm a bit late to this, but for searches, here is how I did what you are asking about in C sharp
private string[] splitString(string stringToSplit)
{
char[] characters = stringToSplit.ToCharArray();
List<string> returnValueList = new List<string>();
string tempString = "";
bool blockUntilEndQuote = false;
int characterCount = 0;
foreach (char character in characters)
{
characterCount = characterCount + 1;
if (character == '"')
{
if (blockUntilEndQuote == false)
{
blockUntilEndQuote = true;
}
else if (blockUntilEndQuote == true)
{
blockUntilEndQuote = false;
}
}
if (character != ',')
{
tempString = tempString + character;
}
else if (character == ',' && blockUntilEndQuote == true)
{
tempString = tempString + character;
}
else
{
returnValueList.Add(tempString);
tempString = "";
}
if (characterCount == characters.Length)
{
returnValueList.Add(tempString);
tempString = "";
}
}
string[] returnValue = returnValueList.ToArray();
return returnValue;
}
Don't reinvent a CSV parser, try FileHelpers.
Try this:
string s = @"111,222,""33,44,55"",666,""77,88"",""99""";
List<string> result = new List<string>();
var splitted = s.Split('"').ToList<string>();
splitted.RemoveAll(x => x == ",");
foreach (var it in splitted)
{
if (it.StartsWith(",") || it.EndsWith(","))
{
var tmp = it.TrimEnd(',').TrimStart(',');
result.AddRange(tmp.Split(','));
}
else
{
if(!string.IsNullOrEmpty(it)) result.Add(it);
}
}
//Results:
foreach (var it in result)
{
Console.WriteLine(it);
}
I needed something a little more robust, so I took from here and created this... This solution is a little less elegant and a little more verbose, but in my testing (with a 1,000,000 row sample), I found this to be 2 to 3 times faster. Plus it handles non-escaped, embedded quotes. I used string delimiter and qualifiers instead of chars because of the requirements of my solution. I found it more difficult than I expected to find a good, generic CSV parser so I hope this parsing algorithm can help someone.
public static string[] SplitRow(string record, string delimiter, string qualifier, bool trimData)
{
// In-Line for example, but I implemented as string extender in production code
Func <string, int, int> IndexOfNextNonWhiteSpaceChar = delegate (string source, int startIndex)
{
if (startIndex >= 0)
{
if (source != null)
{
for (int i = startIndex; i < source.Length; i++)
{
if (!char.IsWhiteSpace(source[i]))
{
return i;
}
}
}
}
return -1;
};
var results = new List<string>();
var result = new StringBuilder();
var inQualifier = false;
var inField = false;
// We add new columns at the delimiter, so append one for the parser.
var row = $"{record}{delimiter}";
for (var idx = 0; idx < row.Length; idx++)
{
// A delimiter character...
if (row[idx]== delimiter[0])
{
// Are we inside qualifier? If not, we've hit the end of a column value.
if (!inQualifier)
{
results.Add(trimData ? result.ToString().Trim() : result.ToString());
result.Clear();
inField = false;
}
else
{
result.Append(row[idx]);
}
}
// NOT a delimiter character...
else
{
// ...Not a space character
if (row[idx] != ' ')
{
// A qualifier character...
if (row[idx] == qualifier[0])
{
// Qualifier is closing qualifier...
if (inQualifier && row[IndexOfNextNonWhiteSpaceChar(row, idx + 1)] == delimiter[0])
{
inQualifier = false;
continue;
}
else
{
// ...Qualifier is opening qualifier
if (!inQualifier)
{
inQualifier = true;
}
// ...It's a qualifier inside a qualifier.
else
{
inField = true;
result.Append(row[idx]);
}
}
}
// Not a qualifier character...
else
{
result.Append(row[idx]);
inField = true;
}
}
// ...A space character
else
{
if (inQualifier || inField)
{
result.Append(row[idx]);
}
}
}
}
return results.ToArray<string>();
}
Some test code:
//var input = "111,222,\"33,44,55\",666,\"77,88\",\"99\"";
var input =
"111, 222, \"99\",\"33,44,55\" , \"666 \"mark of a man\"\", \" spaces \"77,88\" \"";
Console.WriteLine("Split with trim");
Console.WriteLine("---------------");
var result = SplitRow(input, ",", "\"", true);
foreach (var r in result)
{
Console.WriteLine(r);
}
Console.WriteLine("");
// Split 2
Console.WriteLine("Split with no trim");
Console.WriteLine("------------------");
var result2 = SplitRow(input, ",", "\"", false);
foreach (var r in result2)
{
Console.WriteLine(r);
}
Console.WriteLine("");
// Time Trial 1
Console.WriteLine("Experimental Process (1,000,000) iterations");
Console.WriteLine("-------------------------------------------");
watch = Stopwatch.StartNew();
for (var i = 0; i < 1000000; i++)
{
var x1 = SplitRow(input, ",", "\"", false);
}
watch.Stop();
elapsedMs = watch.ElapsedMilliseconds;
Console.WriteLine($"Total Process Time: {string.Format("{0:0.###}", elapsedMs / 1000.0)} Seconds");
Console.WriteLine("");
Results
Split with trim
---------------
111
222
99
33,44,55
666 "mark of a man"
spaces "77,88"
Split with no trim
------------------
111
222
99
33,44,55
666 "mark of a man"
spaces "77,88"
Original Process (1,000,000) iterations
-------------------------------
Total Process Time: 7.538 Seconds
Experimental Process (1,000,000) iterations
--------------------------------------------
Total Process Time: 3.363 Seconds
Here is my fastest implementation based upon string raw pointer manipulation:
string[] FastSplit(string sText, char? cSeparator = null, char? cQuotes = null)
{
string[] oTokens;
if (null == cSeparator)
{
cSeparator = DEFAULT_PARSEFIELDS_SEPARATOR;
}
if (null == cQuotes)
{
cQuotes = DEFAULT_PARSEFIELDS_QUOTE;
}
unsafe
{
fixed (char* lpText = sText)
{
#region Fast array estimatation
char* lpCurrent = lpText;
int nEstimatedSize = 0;
while (0 != *lpCurrent)
{
if (cSeparator == *lpCurrent)
{
nEstimatedSize++;
}
lpCurrent++;
}
nEstimatedSize++; // Add EOL char(s)
string[] oEstimatedTokens = new string[nEstimatedSize];
#endregion
#region Parsing
char[] oBuffer = new char[sText.Length];
int nIndex = 0;
int nTokens = 0;
lpCurrent = lpText;
while (0 != *lpCurrent)
{
if (cQuotes == *lpCurrent)
{
// Quotes parsing
lpCurrent++; // Skip quote
nIndex = 0; // Reset buffer
while (
(0 != *lpCurrent)
&& (cQuotes != *lpCurrent)
)
{
oBuffer[nIndex] = *lpCurrent; // Store char
lpCurrent++; // Move source cursor
nIndex++; // Move target cursor
}
}
else if (cSeparator == *lpCurrent)
{
// Separator char parsing
oEstimatedTokens[nTokens++] = new string(oBuffer, 0, nIndex); // Store token
nIndex = 0; // Skip separator and Reset buffer
}
else
{
// Content parsing
oBuffer[nIndex] = *lpCurrent; // Store char
nIndex++; // Move target cursor
}
lpCurrent++; // Move source cursor
}
// Recover pending buffer
if (nIndex > 0)
{
// Store token
oEstimatedTokens[nTokens++] = new string(oBuffer, 0, nIndex);
}
// Build final tokens list
if (nTokens == nEstimatedSize)
{
oTokens = oEstimatedTokens;
}
else
{
oTokens = new string[nTokens];
Array.Copy(oEstimatedTokens, 0, oTokens, 0, nTokens);
}
#endregion
}
}
// Epilogue
return oTokens;
}
I once had to do something similar and in the end I got stuck with Regular Expressions. The inability for Regex to have state makes it pretty tricky - I just ended up writing a simple little parser.
If you're doing CSV parsing you should just stick to using a CSV parser - don't reinvent the wheel.
Try this
private string[] GetCommaSeperatedWords(string sep, string line)
{
List<string> list = new List<string>();
StringBuilder word = new StringBuilder();
int doubleQuoteCount = 0;
for (int i = 0; i < line.Length; i++)
{
string chr = line[i].ToString();
if (chr == "\"")
{
if (doubleQuoteCount == 0)
doubleQuoteCount++;
else
doubleQuoteCount--;
continue;
}
if (chr == sep && doubleQuoteCount == 0)
{
list.Add(word.ToString());
word = new StringBuilder();
continue;
}
word.Append(chr);
}
list.Add(word.ToString());
return list.ToArray();
}
This is Chad's answer rewritten with state based logic. His answered failed for me when it came across """BRAD""" as a field. That should return "BRAD" but it just ate up all the remaining fields. When I tried to debug it I just ended up rewriting it as state based logic:
enum SplitState { s_begin, s_infield, s_inquotefield, s_foundquoteinfield };
public static IEnumerable<string> SplitRow(string row, char delimiter = ',')
{
var currentString = new StringBuilder();
SplitState state = SplitState.s_begin;
row = string.Format("{0}{1}", row, delimiter); //We add new cells at the delimiter, so append one for the parser.
foreach (var character in row.Select((val, index) => new { val, index }))
{
//Console.WriteLine("character = " + character.val + " state = " + state);
switch (state)
{
case SplitState.s_begin:
if (character.val == delimiter)
{
/* empty field */
yield return currentString.ToString();
currentString.Clear();
} else if (character.val == '"')
{
state = SplitState.s_inquotefield;
} else
{
currentString.Append(character.val);
state = SplitState.s_infield;
}
break;
case SplitState.s_infield:
if (character.val == delimiter)
{
/* field with data */
yield return currentString.ToString();
state = SplitState.s_begin;
currentString.Clear();
} else
{
currentString.Append(character.val);
}
break;
case SplitState.s_inquotefield:
if (character.val == '"')
{
// could be end of field, or escaped quote.
state = SplitState.s_foundquoteinfield;
} else
{
currentString.Append(character.val);
}
break;
case SplitState.s_foundquoteinfield:
if (character.val == '"')
{
// found escaped quote.
currentString.Append(character.val);
state = SplitState.s_inquotefield;
}
else if (character.val == delimiter)
{
// must have been last quote so we must find delimiter
yield return currentString.ToString();
state = SplitState.s_begin;
currentString.Clear();
}
else
{
throw new Exception("Quoted field not terminated.");
}
break;
default:
throw new Exception("unknown state:" + state);
}
}
//Console.WriteLine("currentstring = " + currentString.ToString());
}
This is a lot more lines of code than the other solutions, but it is easy to modify to add edge cases.
