Question

I have a file and I need to filter lines that have (or don’t have) N occurrences of a pattern.
I.e., if my pattern is the letter o and I what to match lines where the letter o occurs exactly 4 times, the expression should match the first of the following example lines but not the others:

foo foo  
foo  
foo foo foo   

I thouth I could do it with a regex in vim, or sed, awk, or any other tool.
I’ve googled and haven’t found anyone that has done a similar thing.
Probably will have do a script or something similar to parse each line.
Does anyone have done a similar thing?

Thanks

Answer 1

A Perl one-liner :

perl -ne 'print if(tr/o/o/ == 4)' foo_file