TIL: sed regex ranges

One can use sed and regular expressions to find chunks of text that span multiple line.

To look for ranges of lines in other words with sed:

sed '/range-start-line-regex/,/range-end-line-regex/ other commands' $file

Example

I'm a Java developer so the example will be from Java world. I was on a support case and we were trying to debug a problem a customer had. As part of the debugging process we've requested the customer to take a number of thread dumps.

The thread dumps we've received contain hundreds of threads. If you don't know, that's how a thread in a thread dump looks like:

"hz.hazelcast.cached.thread-15" #368 prio=5 os_prio=0 tid=0x00007f0634cbb800 nid=0x3fd1 waiting on condition [0x00007f05aa0dd000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x0000000640002c60> (a java.util.concurrent.SynchronousQueue$TransferStack)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(SynchronousQueue.java:460)
	at java.util.concurrent.SynchronousQueue$TransferStack.transfer(SynchronousQueue.java:362)
	at java.util.concurrent.SynchronousQueue.poll(SynchronousQueue.java:941)
	at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1073)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
	at com.hazelcast.util.executor.HazelcastManagedThread.executeRun(HazelcastManagedThread.java:76)
	at com.hazelcast.util.executor.HazelcastManagedThread.run(HazelcastManagedThread.java:92)

   Locked ownable synchronizers:
	- None

I was interested in threads that look like this:

"spring-startup" #65 daemon prio=5 os_prio=0 tid=0x00007f0706f68800 nid=0x624 runnable [0x00007f063911a000]
   java.lang.Thread.State: RUNNABLE
	at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
	at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39)
	at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
	at sun.nio.ch.IOUtil.read(IOUtil.java:197)
	at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380)
	- locked <0x00000006d99b7140> (a java.lang.Object)
  ................................
  at java.lang.Thread.run(Thread.java:748)

In order to find those chunks of text in dozen of files with thousands lines of thread stacks I used sed:

for file in $(find .. -name "threads.*.txt"); do \
  sed -En '/^"spring-startup".*$/,/^[[:space:]]*$/ p' $file> $(basename $file);
done

Here I go through files and for each file I ask sed to find ranges of lines which start with line that matches ^"spring-startup".*$ and ends with line that matches ^[[:space:]]*$ and print them: p

As result I have bunch of files that contain only stack traces for spring-startup threads.