Regex or java solution for parsing this string

Question

I am entering the command show vlan and receiving data in this format, it is one string:

switch# show vlan
VLAN Name                             Status    Ports                           
---- -------------------------------- --------- ------------------------------- 
1    default                          Active    Fa1/0, Fa1/1, Fa1/4, Fa1/6      
                                                Fa1/7, Fa1/8, Fa1/9, Fa1/10     
                                                Fa1/11, Gi0                     
2    VLAN0002                         Active                                    
3    VLAN0003                         Active    Fa1/5                           
6    VLAN0006                         Active                                    
999  VLAN0999                         Active    Fa1/2, Fa1/3
switch# 

I wish to make new strings that start with the number of the vlan and end when it reaches the VLAN number. So the Strings here would be:

(1)    1    default                          Active    Fa1/0, Fa1/1, Fa1/4, Fa1/6      
                                                       Fa1/7, Fa1/8, Fa1/9, Fa1/10     
                                                       Fa1/11, Gi0                     
(2)    2    VLAN0002                         Active                                    
(3)    3    VLAN0003                         Active    Fa1/5                           
(4)    6    VLAN0006                         Active                                    
(5)    999  VLAN0999                         Active    Fa1/2, Fa1/3

What would I do here, a regex that tests for a number followed by a white space but with a \r or \n before it? Or similar in java using .charAt(i) etc? and then substring it?

The I need to split each of these strings into tokens with a white space delimiter. I would use a for loop to go through each string I guess.

I tried splitting at \r\n if it is followed by a digit, was this right?

String[] parts = finalCommand.split("\r\n?=\\d");

but it doesn't work?! I really can't see why.

Answer 1

I don't think split() is the tool you're looking for. Check this out:

List<String> matchList = new ArrayList<String>();
Pattern p = Pattern.compile("(?m)^\\d+.*$(?:\r?\n(?!\\S).*$)*");
Matcher m = p.matcher(s);
while (m.find()) {
    matchList.add(m.group());
} 

As you said, continuation lines are characterized by whitespace following the line separator. This regex identifies them by doing a negative lookahead for a non-whitespace character (\S) immediately after the line separator.

The (?m) turns on multiline mode, allowing ^ and $ to match the beginning and end of individual lines. Note that it's the carriage return (\r) that's optional in the line separator, not the linefeed (\n).

Answer 2

Answer was pretty simple, was some sort of brackets problem

This doesn't work:

String[] parts = finalCommand.split("\r\n?=\\d");

This does:

String[] parts = finalCommand.split("(\r\n)(?=\\d)");

Answer 3

I tried splitting at \r\n if it is followed by a digit, was this right?

String[] parts = finalCommand.split("\r\n?=\\d");

but it doesn't work?! I really can't see why.

If finalCommand is after you've already stripped off the leading #switch\r\n and trailing \r\nswitch#, and if the lines in finalCommand are indeed separated by \r\n, then — yes, that's almost right. The only thing you need to change is, you need to write (?=\d) rather than ?=\d: the parentheses are part of the syntax for a lookahead assertion. (Otherwise \n?= is interpreted as "an optional \n, followed by =.) So:

String[] parts = finalCommand.split("\r\n(?=\\d)");