文件: test.txt

"http-nio-8888-exec-3" #30 daemon prio=5 os_prio=0 tid=0x00007f9c10f39800 nid=0x687a waiting on condition [0x00007f9bde0ed000]
   java.lang.Thread.State: WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x00000000eca402c0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
	at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
	at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:108)
	at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:33)
	at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

   Locked ownable synchronizers:
	- None

比如我想获取关键字 concurrent 及后面 6 个字符，那么可以用以下命令:

# 这里的 16 是: concurrent 占用 10 个字符，外加后面的 6 个字符
cat test.txt | awk '{ if(match($0,"concurrent")) { print substr($0,RSTART,16) }}'

获取效果如下:

root@dreamboy:~/test# cat test.txt | awk '{ if(match($0,"concurrent")) { print substr($0,RSTART,16) }}'
concurrent.locks
concurrent.locks
concurrent.locks
concurrent.Linke
concurrent.Threa
concurrent.Threa
concurrent.Threa
root@dreamboy:~/test# 

如果不想要 concurrent 关键字，可以使用:

cat test.txt | awk '{ if(match($0,"concurrent")) { print substr($0,RSTART+RLENGTH,6) }}'

补充资料 - awk 内置变量