UNIX - 使用egrep，如何過濾發生n次的模式？

Question

標題說明了一切，我需要過濾一個具有規格的egrep文件，但我無法弄清楚的是確保它發生3次。 （從問題的直接措辭 - 包含5個或更多字符的話，這至少發生三次行）

Answer 1

隨着awk（未測試）：

awk ' 
    /\b[a-zA-Z]{5}\b/{ 
    matches[$0]++ 
    } 
    END{ 
    for (m in matches) { 
     if (matches[m] >= 3) {print m} 
    } 
    } 
' file 

Answer 2

egrep '([a-zA-Z]{5}).*\1.*\1' 

這工作在我快速測試，但我不知道它是

\1（和\2，\3 ...）如何強大的是反向引用。我放置了(和)五個字母的模式，[a-zA-Z]，這被稱爲第一個捕獲組。 \1則意味着正則表達式希望找到在第一組中匹配的相同單詞的重複。

最後，有三個詞之間的.*，以允許任何在它們之間出現

Answer 3

$ cat ip.txt 
abc abc abc should not match 
totally this line should totally match, isn't it? totally 
Title: word with 5 letters like title should also match, given title is present 3 or more times 
this line should not totally match, total only partly matches with totally 

，以配合匹配情況下的話：無論情況

$ grep -wE '([a-zA-Z]{5,}).*\1.*\1' ip.txt 
totally this line should totally match, isn't it? totally 

要匹配的話：

$ grep -iwE '([a-zA-Z]{5,}).*\1.*\1' ip.txt 
totally this line should totally match, isn't it? totally 
Title: word with 5 letters like title should also match, given title is present 3 or more times 

匹配任意五個或更多字母的序列：

$ grep -iE '([a-zA-Z]{5,}).*\1.*\1' ip.txt 
totally this line should totally match, isn't it? totally 
Title: word with 5 letters like title should also match, given title is present 3 or more times 
this line should not totally match, total only partly matches with totally 

• -E擴展正則表達式
• -w匹配全字
• -i忽略大小寫
• [a-zA-Z]{5,}小寫或大寫字母，五次或更多次
• ()捕獲組和\1被回去參考它

和一點樂趣，如果你有pcre正則表達式

$ echo 'totally title match' | grep -P '([a-zA-Z]{5,}).*(?1).*(?1)' 
totally title match 

• (?1)指的是正則表達式模式([a-zA-Z]{5,})本身