匹配线与图案n次在同一行 [英] Match lines with pattern n times in the same line

问题描述

我有一个文件，我需要过滤模式的有（或没有）第N发生。
也就是说，如果我的模式是信 0 ，我什么以匹配信 0 恰好出现4次线，恩pression应与其他第一下面的示例中的行而不是：

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   

我thouth我可以在vim正则表达式做到这一点，还是用sed，awk中，或任何其他工具。
我GOOGLE了，并没有发现任何人，也做了类似的事情。
将可能有做一个脚本或类似分析每一行的东西。
有没有人做过类似的事情？

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?

感谢

推荐答案

一个Perl的单行：

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

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