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誰能詳細解釋一下下面兩個命令正規表示式

tag-icon • tag-icon sed grep regular-expression
誰能詳細解釋一下下面兩個命令正規表示式

以下兩個指令用於計算文字檔案中第二列的非零整數的數量。誰能詳細解釋一下正規表示式。

grep -c '^[^,]*,[^0][^,]*,' < myfile.txt
sed '/^[^,]*,0,.*/d' < myfile.txt | sed -n '$='

答案1

第一個正規表示式搜尋包含以下內容的任何行：

'^        - start of line, followed by
 [^,]*    - 0 or more non-comma characters, followed by
 ,        - a comma, followed by
 [^0]     - any single character other than a zero, followed by
 [^,]*    - 0 or more non-comma characters, followed by
 ,'       - a comma

grep -c 統計匹配行數

第二個正規表示式匹配

'/        (the start of the regex)
 ^        - start of line, followed by
 [^,]*    - 0 or more non-comma characters, followed by
 ,0,      - a comma then a zero then a comma, followed by
 .*       - 0 or more other characters
 /d'      (the end of the regex -- delete the lines matching the preceding expression)

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