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`grep` 查找符合多个条件的单词（用于拼字游戏）

tag-icon • tag-icon command-line mac grep
`grep` 查找符合多个条件的单词（用于拼字游戏）

我正在使用下载的名为“sowpods.txt”的拼字游戏单词列表，并尝试使用它grep来查找符合以下条件的所有单词：

  • 7 个字母的单词
  • 以同一个字母开头和结尾
  • 第二、第四和第六个字母相同
  • 第 3 和第 5 个字母不同

我目前为止

grep -i "^(.).*\1$" sowpods.txt > output.txt

给出了反向引用错误，所以我尝试使用在线指南，但它们非常令人困惑。这可能吗？如果可以，有人能帮忙吗？

我在 Mac 上并使用默认终端。

答案1

-P如果您的系统上可用，请使用选项（PCRE）：

grep -P '^(?=[a-zA-Z]{7}$)(.)(?!\1)(.)(?!\1)(?!\2)(.)\2(?!\1)(?!\2)(?!\3).\2\1$' inputfile

解释：

^
  (?=[a-zA-Z]{7}$)  : positive lookahead, zero-length assertion that make sure we have exactly 7 letters. You may use \pL{7} if you want to deal with any laguage
  (.)               : first letter, captured in group 1
  (?!\1)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 1 after
  (.)               : second letter, captured in group 2
  (?!\1)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 1 after
  (?!\2)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 2 after
  (.)               : third letter, captured in group 3
  \2                : fourth letter == second letter
  (?!\1)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 1 after
  (?!\2)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 2 after
  (?!\3)            : negative lookahead, zero-length assertion that make sure we don't have the same letter as in group 3 after
  .                 : fifth letter
  \2                : sixth letter == second letter
  \1                : seventh letter == first letter
$

演示

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