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May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
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Read multiple lines of a file based on regex matching a single line

Terminal - Read multiple lines of a file based on regex matching a single line
for i in `grep -n "SomeRegEx" foo.txt | sed 's/:/ /' | awk '{print $1}'`; do echo "head -n `echo "$i+4" | bc` foo.txt | tail -n 5"; done > headsandtails.sh
2010-07-01 05:48:02
User: reklis
Functions: awk echo sed
Read multiple lines of a file based on regex matching a single line

Finds the line number matching the regex, then passes that to BC for some math, passes that to head, and uses tail to trim off the unwanted section at the top. The whole thing is spit out to a script that can then be shared or run. Comes in handy for reading select sections from error logs.


There are 9 alternatives - vote for the best!

Terminal - Alternatives

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What others think

My god that's complicated. First of all, we don't need the awk bit, this will do:

| sed 's/:.*// |

If you're using bash, you can get rid of echo and bc, too:


Also, head and tail are a bit inefficient, so let's use sed again:

sed -n $i,$((i+4))p


sed -n $i,+4p

But sed can do regexes too, so now we can replace the whole command with:

sed -n '/SomeRegEx/,+4p' foo.txt

No need for a script :-)

Comment by flatcap 403 weeks ago

Or egrep:

egrep "SomeRegEx" -A 4 foo.txt


-A print lines after match

-B print lines after match

-C print lines before and after match (e.g 4 before and 4 after)

Comment by quincymd 403 weeks ago

Your point of view

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