Working w/ regular expressions

Question

Hi all,
I'm having trouble figuring out what regular expression to use to parse my output. I want to capture a block of text that starts with a tab (\t) and ends with a line containing the word "error code."
For example, if my output is the following: ( [\tab] denotes ASCII tab character)
[\tab]Some command
Anytext
Anytext
blah blah error code is 0
[\tab]Some other command
[\tab]Yet another command
Anytext
blah blah error code is 1
I would like subsequent calls to matcher.find() to find these two blocks:
[\tab]Some command
Anytext
Anytext
blah blah error code is 0
and
[\tab]Yet another command
Anytext
blah blah error code is 1
I thought the regular expression should be something like
"[\t](.*\n)+.*error code.*"
but the above regular expression returns the entire text intead of the two "blocks" that I want. I know that Java returns the longest match for the expression but I don't know how to exclude "error code" in the middle...
"[\t](.*\n)+(.*error code.*){1}" ???
Any help is greatly appreciated.
Thanks,
KK

Answer 1

..but I'm not sure what is the purpose of the second part (?:\\n|\\Z).
Would someone care to explain this too me?This non-capturing group is for final delimiter, it means "last character is a Line Feed char or end of input reached", just to prevent error if last line is an error line without Line Feed char.
A good reference about groups are at JRegex documentation/examples:
http://jregex.sourceforge.net/.
Good news for you: the minimal regular expression that solves your problem.
import java.io.*;
import java.util.*;
import java.util.regex.*;
public class ParseTest {
public static void main(String[] args) throws Exception {
String Output =
"\t\tgcc -someoption file0\n"
+ "\t\tgcc -someoption file1\n"
+ "\t\tgcc -someoption file2\n"
+ "\t\tgcc -someoption file3\n"
+ "some error message\n"
+ "some more error message\n"
+ "make: 1254-004 The error code from the last command is 1.\n"
+ "make: 1254-005 Ignored error code 1 from last command.\n"
+ "\t\tgcc -someoption file4\n"
+ "\t\tgcc -someoption file5\n"
+ "error message\n"
+ "more error message\n"
+ "make: 1254-004 The error code from the last command is 1.\n"
+ "make: 1254-005 Ignored error code 1 from last command.\n"
+ "\t\tgcc -someoption file6\n"
+ "\t\tgcc -someoption file7\n"
+ "last error message\n"
+ "make: 1254-005 Ignored error code 1 from last command.";
System.out.println(Output+"\n");
final String
// Regular Expression pattern to find only commands with error messages.
// $1 = command
// $2 = error message
re = "\\t+(.+)\\n([^\\t]+[^\\t\\n])(?:\\n|$)";
Pattern p = Pattern.compile(re);
System.out.println("Pattern:\n"+p.pattern());
Matcher m = p.matcher(Output);
for (int j=1; m.find(); j++) {
System.out.println("\nMatching "+j+":\n");
System.out.println("--------------------------------");
System.out.println(m.group(1));
System.out.println("--------------------------------");
System.out.println(m.group(2));
System.out.println("--------------------------------");
Regards.