Question

I’m trying to get matches for commands like this;

[AUTR| <version_software> | <version_protocol> | <msg> ]
[PING]

What is the regular expression that find this matches for the first command?

AUTR
version_software
version_protocol
msg

this is the code that parse that:

String[] tokens =  msg.replace('<',' ').replace('>',' ').replace('[', ' ').replace(']', ' ').split("\\|");
for (int i=0; i<tokens.length; i++) tokens[i] = tokens[i].trim();

I’m only wondering how it can be done with a regex solution.

EDIT:

I’m trying to match groups with easier expressions, and with this code the call to m.groupCount returns one… but when I try to print it… it throws this exception “java.lang.IllegalStateException: No match found”

    Pattern pattern = Pattern.compile("([\\w+])");
    Matcher m = pattern.matcher("[AUTR]");

    for (int i=0; i<m.groupCount();i++)
    {
        System.out.println(m.group(i));
    } 

Answer 1

EDIT:
http://fiddle.re/6ykc

Regular Expression:

\[([\w]+)(\s*\|\s*<([\w. ]+)>\s*)*\]

Java Regex String:

"\\[([\\w]+)(\\s*\\|\\s*<([\\w. ]+)>\\s*)*\\]"

Note that this is for variable commands now and that all extra parameters must match the following character set [a-zA-Z_0-9. ] (Includes periods and spaces).

Issue: There is an issue with variable length commands that you cannot capture more than one group with a variable type grouping.

The captured input associated with a group is always the subsequence that the group most recently matched. If a group is evaluated a second time because of quantification then its previously-captured value, if any, will be retained if the second evaluation fails. Matching the string “aba” against the expression (a(b)?)+, for example, leaves group two set to “b”. All captured input is discarded at the beginning of each match.
http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html#cg

EDIT 2:

In order to get all of them you can do 2 regular expressions, one to grab the command:

String command_regex = "\\[([\\w]+)";

And find that and then find the parameters which you can use the <> as your key character to select:

String parameters = "<([\\w. ]+)>";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(string_to_match);

while (matcher.find()) {
    System.out.println(matcher.group());
}

Hope that helps.

---

ORIGINAL:

Not exactly sure on the formatting, are the “<” and “>” and “|” required? And what are the formats for the command, version_software, version_protocol and message? This is my attempt though for regular expressions (tested in Python)

\[(\w+)\s*\|\s*<([\w.]+)>\s*\|\s*<(\w+)>\s*\|\s*<([\w\s]+)>\s*\]

You need to make sure to escape the brackets and the pipe symbols (I added \s* conditions between because I don’t know if there will be spaces or not. If you do:

>> search.re("expression above", line) 
>> search.groups()

It should give all tokens in python at least. I left it more hardcoded to allow room for adjustments on each token you wanted to grab, otherwise you could reduce the last 3 parts by making it a group and saying to repeat 3 times. Let me know results?