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问题:
I want to remove a pattern with sed, only at second occurence. Here is what I want, remove a pattern but on second occurrence.
What's in the file.csv:
a,Name(null)abc.csv,c,d,Name(null)abc.csv,f
a,Name(null)acb.csv,c,d,Name(null)acb.csv,f
a,Name(null)cba.csv,c,d,Name(null)cba.csv,f
Output wanted:
a,Name(null)abc.csv,c,d,Name,f
a,Name(null)acb.csv,c,d,Name,f
a,Name(null)cba.csv,c,d,Name,f
This is what i tried:
sed -r 's/(\(null)\).*csv//' file.csv
The problem here is that the regex is too greedy, but i cannot make is stop.
I also tried this, to skip the first occurrence of "null":
sed -r '0,/null/! s/(\(null)\).*csv//' file.csv
Also tried but the greedy regex is still the problem.
sed -r 's/(\(null)\).*csv//2' file.csv
I've read that ?
can make the regex "lazy", but I cannot make it workout.
sed -r 's/(\(null)\).*?csv//' file.csv
回答1:
The more robust awk solution:
Extended sample file input.csv
:
12,Name(null)randomstuff.csv,2,3,Name(null)randomstuff.csv, false,Name(null)randomstuff.csv
12,Name(null)AotherRandomStuff.csv,2,3,Name(null)AotherRandomStuff.csv, false,Name(null)randomstuff.csv
12,Name(null)alphaNumRandom.csv,2,3,Name(null)alphaNumRandom.csv, false,Name(null)randomstuff.csv
The job:
awk -F, '{ c=0; for(i=1;i<=NF;i++) if($i~/\(null\)/ && c++==1) sub(/\(null\).*/,"",$i) }1' OFS=',' input.csv
The output:
12,Name(null)randomstuff.csv,2,3,Name, false,Name(null)randomstuff.csv
12,Name(null)AotherRandomStuff.csv,2,3,Name, false,Name(null)randomstuff.csv
12,Name(null)alphaNumRandom.csv,2,3,Name, false,Name(null)randomstuff.csv
回答2:
sed
does provide an easy way to specify which match to be replaced. Just add the number after delimiters
$ sed 's/(null)[^.]*\.csv//2' ip.csv
a,Name(null)abc.csv,c,d,Name,f
a,Name(null)acb.csv,c,d,Name,f
a,Name(null)cba.csv,c,d,Name,f
$ # or [^,] if there are no , within fields
$ sed 's/(null)[^,]*//2' ip.csv
a,Name(null)abc.csv,c,d,Name,f
a,Name(null)acb.csv,c,d,Name,f
a,Name(null)cba.csv,c,d,Name,f
Also, no need to escape ()
when not using extended regular expressions
回答3:
Execute:
awk '{sub(/.null.....csv,f/,",f")}1' file
And the output should be:
a,Name(null)abc.csv,c,d,Name,f
a,Name(null)acb.csv,c,d,Name,f
a,Name(null)cba.csv,c,d,Name,f