CODEWITHSUNDEEP
c#regexparsing
CaptainNemo
CaptainNemo

Reputation: 1552

Using Regex to match commands and extract parameters

I'm looking for an easy way (for the person who will be entering all the information about the commands and parameters) to match commands out of a list of commands and extract specific parameters from it. For example this two commands: SENDDR456 (where 456 is the parameter) GETmsg35 (where msg and 35 are two parameters) I thought regex is the best option. The goal again is to make the identifier\extractor scalable and allow for easily adding more commands. I'm using C#.

Upvotes: 0

Views: 235

Answers (3)

Charlie
Charlie

Reputation: 4895

If the Information lies in strings with different styles,lengths or offsets, Regex is surely the best solution.

Here there are just two commands, SENDDR and GET that can be checked via substring Function but again the length of parameter is not the same every time so you will have to check it by digits and alphabets .In this case Regex is easy than implementing all this.

Here is the regex assuming parameters are numbers or either small letters

       (SENDDR|GET)(\d+|[a-z]+)+

Upvotes: 0

Adil
Adil

Reputation: 148110

Assuming your command is upper case and parameter are lowercase or number, you can use (\\d+)|([a-z]+)

var matches1 = Regex.Matches("GETmsg35", "(\\d+)|([a-z]+)"); 
foreach(Match match in matches1)
   Console.WriteLine(match.Value);

To include command you can use ([A-Z]+)|([a-z]+)|(\\d+)

var matches1 = Regex.Matches("GETmsg35", "([A-Z]+)|([a-z]+)|(\\d+)");   
if(matches1.Count > 0)     
      Console.WriteLine("Command >> " + matches1[0].Value);
for(int i=1; i < matches1.Count; i++)
   Console.WriteLine("Parameters >> " + i + "\t" + matches1[i].Value);

Output

Command >> GET
Parameters >> 1  msg
Parameters >> 2  35

Upvotes: 0

zx81
zx81

Reputation: 41838

.NET CaptureCollection Can Tokenize

But It Depends on Whether Consecutive Parameters Can Be Well-Delimited or Well-Specified

For your example, you can use this regex:

(SENDDR|GET)(\d+|[a-z]+)+

This relies on the terrific CaptureCollection specific to .NET regex, whereby when a given capture group is quantified, all the intermediate captures are preserved in a stack and accessible.

  • Groups[1].Value contains the command
  • The capture Group 2 contains the parameters in a capture collection: Groups[2].Captures[0].Value contains the first parameter, Groups[1].Captures[1].Value contains the second parameter

But note that this relies on the parameters being well-specified or delimited. For instance, in this example, one parameter is specified by [a-z]+, the other by \d+, which are mutually exclusive.

Upvotes: 1

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