How to Grep Different words in Different lines in Linux

Question

I am trying to monitor a log using tail -f command and when ever I come across two different words in different lines on same log, need to capture those and send a email notification:

For example: cat example.txt:

<event> 12345 </event>
<Description> Exception on file transfer for user ABC </Description>

I need to monitor for event '12345' having 'Exception' for user 'ABC'.

When I do tail -F example.txt | egrep "12345|Exception|ABC" This command prints if it sees any one of Grep keyword. Instead it needs to print only if it comes across all keywords in grep.

Possible duplicate of How to find patterns across multiple lines using grep? — Marcus
– Marcus, Commented Mar 15, 2019 at 19:45
Also see How to use grep to match string1 AND string2? and How to grep for two words existing on the same line? — jww
– jww, Commented Mar 15, 2019 at 20:22

altagir · Accepted Answer · 2019-03-15 19:46:33Z

1

try

tail -f example.txt | egrep --line-buffered  "Exception.*ABC" -B 1 | egrep -v Description

"Exception.*ABC" search for lines having Exception AND ABC
"-B 1" is to have previous line (the event)
"--line-buffered" is to turn grep buffering mode (else the second egrep won't process)
"| egrep -v Description" finally removes the Description line (since you just want the event)

you will end up having

    <event> 12345 </event>

Play with each parameter to see the difference

regards

answered Mar 15, 2019 at 19:46

altagir

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1 Comment

Anvesh Over a year ago

Thank You @altagir. This helped

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