CODEWITHSUNDEEP
awk
mlowry
mlowry

Reputation: 171

Print lines matching a pattern only if the next line does not match the pattern

I want to use awk to print lines that match a pattern only if the following line does not match the pattern. In this case, the pattern is that the line begins with O. This is what I tried:

awk '!/^O/ {print x}; /^O/ {x=$0}' myfile.txt

This is printing far too many lines though, including printing the lines I specifically do not want to print.

Upvotes: 0

Views: 868

Answers (1)

user3442743
user3442743

Reputation:

Not tested. Should probz work

awk '/^O/{if(seen==0){seen=1};c=$0} !/^O/{if (seen==1) {print c; seen=0;}}' myfile.txt

Shortened version

 awk '/^O/{x=$0} !/^O/{if(x!=0) {print x; x=0;}}' myfile.txt

More shortening

awk '/^O/{x=$0} !/^O/{if(x){print x;x=0;}}' myfile

Think this is shortest it can go

awk '/^O/{x=$0} !/^O/&&x{print x;x=0;}' myfile

Changed them all because it printed the wrong lines.

also made it shorter :)

awk 'a=/^O/{x=$0} !a&&x{print x;x=0;}' myfile

Upvotes: 1

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