Grep surrounding lines
13 Aug 2013
Today I was scanning the logs of one our node apps because a client was having issues. I wanted to find all of the lines before any line with the string ‘500 -‘ because this is where the exceptions actually start spitting out their stack trace. Turns out this is really easy with grep.
The trick is with these flags:
Context control: -B, --before-context=NUM print NUM lines of leading context -A, --after-context=NUM print NUM lines of trailing context -C, --context=NUM print NUM lines of output context
Example of how to use grab 20 lines prior to the 500’s:
tail -n 10000 | grep -B 20 '500 -'
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