Help me to split string using RegExp

Question

please help me this problem. I want to split "-action=1" to "action" and "1".

string pattern = @"^-(\S+)=(\S+)$";
Regex regex = new Regex(pattern);
string myText = "-action=1";
string[] result = regex.Split(myText);

I don't know why result have length=4.

result[0] = ""
result[1] = "action"
result[2] = "1"
result[3] = ""

Please help me.

P/S: I am using .NET 2.0.

Thanks.

Hello, I tested with string: @"-destination=C:\Program Files\Release" but it have inaccurate result, I don't understand why result's length = 1. I think because it has a white space in string.

I want to split it to "destination" & "C:\Program Files\Release"

More info: This is my requirement: -string1=string2 -> split it to: string1 & string2. In string1 & string2 don't contain characters: '-', '=', but they can contain white space.

Please help me. Thanks.

Hello, I tested with string: @"-destination=C:\Program Files\Release" but it have inaccurate result, I don't understand why result's length = 1. I think because it has a white space in string. I want to split it to "destination" & "C:\Program Files\Release" Please help me. Thanks. — Leo Vo
– Leo Vo, Commented Jan 20, 2010 at 11:39

Lucero · Accepted Answer · 2010-01-20 10:19:58Z

5

Don't use split, just use Match, and then get the results from the Groups collection by index (index 1 and 2).

Match match = regex.Match(myText);
if (!match.Success) {
    // the regex didn't match - you can do error handling here
}
string action = match.Groups[1].Value;
string number = match.Groups[2].Value;

answered Jan 20, 2010 at 10:19

Lucero

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3 Comments

Timothy Khouri Over a year ago

You should never use groups by index in .NET Regex... you can name the groups for a reason. Imagine if someone slightly changed the regex later by adding another set of parenthesis. Then you'd have to change all your indexes everywhere. - Use group names instead.

Lucero Over a year ago

I only use indexes for very simple cases, such as this one (just one or two captures, no nested groups, etc.). Otherwise, I agree that using names makes the regex much more robust and easier to understand.

Leo Vo Over a year ago

Hello, I tested with string: @"-destination=C:\Program Files\Release" but it have inaccurate result. I think because it has a white space in string. I want to split it to "destination" & "C:\Program Files\Release"

Rubens Farias · Accepted Answer · 2010-01-20 13:21:29Z

3

Try this (updated to add Regex.Split):

string victim = "-action=1";
string[] stringSplit = victim.Split("-=".ToCharArray());
string[] regexSplit = Regex.Split(victim, "[-=]");

EDIT: Using your example:

string input = @"-destination=C:\Program Files\Release -action=value";
foreach(Match match in Regex.Matches(input, @"-(?<name>\w+)=(?<value>[^=-]*)"))
{
    Console.WriteLine("{0}", match.Value);
    Console.WriteLine("\tname  = {0}", match.Groups["name" ].Value);
    Console.WriteLine("\tvalue = {0}", match.Groups["value"].Value);
}
Console.ReadLine();

Of course, this code have issues if your path contains - character

edited Jan 20, 2010 at 13:21

answered Jan 20, 2010 at 10:20

Rubens Farias

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Comments

Timothy Khouri · Accepted Answer · 2010-01-20 10:24:05Z

3

In .NET Regex, you can name your groups.

string pattern = @"^-(?<MyKey>\S+)=(?<MyValue>\S+)$";
Regex regex = new Regex(pattern);
string myText = "-action=1";

Then do a "Match" and get the values by your group names.

Match theMatch = regex.Match(myText);
if (theMatch.Success)
{
    Console.Write(theMatch.Groups["MyKey"].Value); // This is "action"
    Console.Write(theMatch.Groups["MyValue"].Value); // This is "1"
}

answered Jan 20, 2010 at 10:24

Timothy Khouri

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Comments

ZombieSheep · Accepted Answer · 2010-01-20 10:18:27Z

0

What's wrong with using string.split()?

string test = "-action=1";
string[] splitUp = test.Split("-=".ToCharArray());

I admit, though that this still gives you possibly more parameters than you'd like to see in the split up array...

[0] = ""
[1] = "action"
[2] = "1"

answered Jan 20, 2010 at 10:18

ZombieSheep

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2 Comments

Lucero Over a year ago

What's wrong? You don't get input validation for free, and it may handle things differently (imagine -range=1-2).

ZombieSheep Over a year ago

Granted, but with RegEx, you don't get anything for free, and as the OP has seen, it is not a trivial task to build the appropriate regex string. I'm just suggesting a reasonably workable alternative that doesn't rely on knowing the unknown (see OP's edit)

Community · Accepted Answer · 2017-05-23 11:48:36Z

0

In his talk Regular Expression Mastery, Mark Dominus attributes the following helpful rule to Learning Perl author (and fellow StackOverflow user) Randal Schwartz:

Use capturing or m//g [or regex.Match(...)] when you know what you want to keep.

Use split when you know what you want to throw away.

edited May 23, 2017 at 11:48

CommunityBot

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answered Jan 20, 2010 at 14:31

Greg Bacon

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