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sed to conditionally delete multiple lines

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# 1  
Old 06-22-2011
sed to conditionally delete multiple lines
Hello

I'd like to remove any line in an output file that is preceded by one or more warning messages (each warning is on a separate line).

Example :
Code:
WARNING: Estimation of lower confidence limit of \rho failed; setting it to 0.
822     28447                                                                   1.51e+05        0.00e+00<-8.66e-04<9.52e-03
WARNING: Estimation of lower confidence limit of \rho failed; setting it to 0.
823     28343                                                                   1.50e+05        0.00e+00<-8.82e-04<1.97e-02
WARNING: Estimation of lower confidence limit of \rho failed; setting it to 0.
WARNING: Estimation of upper confidence limit of \rho failed; setting it to 1.
824     28246                                                                   1.50e+05        0.00e+00<-5.84e-04<1.21e-03

All these lines should be deleted ; there can be more than 2 warnings, in which case the output line should be deleted as well.

A command like
Code:
sed '/WARNING/{N; //d}' SlFf.rho2

doesn't work for even numbers of warning messages.

I'm not familiar enough to the n, N, d, and D commands to figure out their behaviour. Any ideas ?

Thanks
jos
# 2  
Old 06-22-2011
an awk version:

Code:
 
awk '/WARNING/ {c=1;next} c==1 { c=0;next} 1' input_file
aa
bb
dd
dd
ee

# 3  
Old 06-22-2011
Code:
$ cat <<EOF | awk '/WARNING/ { W=2; } {} ((W--)<=0)'

WARNING
WARNING
DANGER WILL ROBINSON
DANGER DANGER
WARNING
THIS IS NOT A DRILL
THIS IS NOT A DRILL
THIS IS NOT A DRILL
THIS IS NOT A DRILL
EOF

DANGER DANGER
THIS IS NOT A DRILL
THIS IS NOT A DRILL
THIS IS NOT A DRILL
$

Every line that matches WARNING sets W=2. Every line, whether it matches or not, decrements W. So a matching line in effect sets it to 1. The statement at the end of the {} prevents printing when W > 0, which avoids one or more warning lines in a row plus one line after. You could change W=2 to W=3 if you wanted to skip two lines after.
These 2 Users Gave Thanks to Corona688 For This Post:
alister jossojjos
# 4  
Old 06-22-2011
Great, thanks !
It would definitely have taken a lot of time before I would have figured out that one can use awk this way ...
# 5  
Old 06-22-2011
Thank you, Corona688. Your sample data made me laugh.
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