Regular Expression to match two strings in AND condition

Question

I am new to regular expression, please kindly help me on the error scenario where I need to use regex to match two error messages (appearing in different lines, but same paragraph) in AND condition from a log file:

Msg1 - ERROR [com.company.util.ejb.TimedBean] () FAILED processing Loader

Msg2 - java.lang.RuntimeException: Message code:[SL] is unknown.

Basically, what I need is to match (msg1)&&(msg2), in this case, (ERROR...Loader) will appear in the first line and (java...unknown) will follow in the next line. The messages will always follow this order. I am not programming in any typical language here, they will be put into a enterprise tool that accepts regexp.

If possible, would you also show me how to make it in Or condition as (msg1)||(msg2)?

It is not clear what you want to achieve ... Can you explain betteR ? — aleroot
– aleroot, Commented Jun 4, 2012 at 19:34

csd · Accepted Answer · 2012-06-04 20:15:04Z

Matching two consecutive lines is, in theory, just a matter of putting the two regular expressions end-to-end. So for purposes of illustration, let's say you've got a file named logfile.txt that contains messages you're looking for. Then from a Linux command line you could do something like this:

pcregrep -M -o '^ERROR\N*Loader$\njava\N*unknown\.$\n' logfile.txt

and it would print the line pairs that you're looking for. Breaking it down into parts:

^ERROR matches the word ERROR at the beginning of a line.
\N* matches any number of characters that aren't a line terminator.
Loader$ matches the word Loader at the end of a line.
\n matches the newline character. (Might be different on Windows.)
java\N*unknown\.$\n is more of the same.

BUT... And this is a big problem... The tool that handles your regular expression must be capable of doing multi-line matches, and that capability must be turned on. (That's what the -M command line option to pcregrep enables.) Many regexp tools, such as plain grep on many systems, can't do multiline searches. So you may be out of luck.

Thanks csd. I don't know why but "\N" doesn't work in my tool (maybe I didn't put it in the right way). I was able to enable the multi-line match feature. The final regexp I used was /(ERROR.*\n).+(java\.lang\.RuntimeException\: Message code\:\[SL\] is unknown.*\n)/i - it doesn't look as efficient as yours, but works for me!
Hmm... Here is a better one: /ERROR.+java\.lang\.RuntimeException\: Message code\:\[SL\] is unknown/s
If \N isn't supported, you could write it as [^\n] (i.e. the class of characters that isn't \n). The reason you might want to do it that way (instead of just using .+) is that you don't want your regular expression to match from the top of your file down to the last match at the bottom.

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