bash 使用grep检测重复字符
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Detect repeated characters using grep
提问by Unknown
I'm trying to write a grep (or egrep) command that will find and print any lines in "words.txt" which contain the same lower-case letter three times in a row. The three occurrences of the letter may appear consecutively (as in "mooo") or separated by one or more spaces (as in "x x x") but not separated by any other characters.
我正在尝试编写一个 grep（或 egrep）命令，该命令将在“words.txt”中查找并打印任何连续三次包含相同小写字母的行。出现的三个字母可以连续出现（如“mooo”）或由一个或多个空格分隔（如“xx x”）但不由任何其他字符分隔。
words.txt contains:
words.txt 包含：
The monster said "grrr"!
He lived in an igloo only in the winter.
He looked like an aardvark.
Here's what I think the command should look like:
这是我认为命令应该是这样的：
grep -E '\b[^ ]*[[:alpha:]]{3}[^ ]*\b' 'words.txt'
Although I know this is wrong, but I don't know enough of the syntax to figure it out. Using grep, could someone please help me?
虽然我知道这是错误的，但我对语法的了解还不够多。使用grep，有人可以帮助我吗？
回答by choroba
Does this work for you?
这对你有用吗？
grep '\([[:lower:]]\) * *'
It takes a lowercase character [[:lower:]]and remembers it \( ... \). It than tries to match any number of spaces _*(0 included), the rememberd character \1, any number of spaces, the remembered character. And that's it.
它需要一个小写字符[[:lower:]]并记住它\( ... \)。然后尝试匹配任意数量的空格_*（包括 0）、记住的字符\1、任意数量的空格、记住的字符。就是这样。
You can try running it with --color=autoto see what parts of the input it matched.
您可以尝试运行它--color=auto以查看它匹配输入的哪些部分。
回答by nshew
Try this. Note that this will not match "mooo", as the word boundary (\b) occurs before the "m".
尝试这个。请注意，这将不匹配“mooo”，因为单词边界 ( \b) 出现在“m”之前。
grep -E '\b([[:alpha:]]) *\1 *\1 *\b' words.txt
grep -E '\b([[:alpha:]]) *\1 *\1 *\b' words.txt
[:alpha:]is an expression of a character class. To use as a regex charset, it needs the extra brackets. You may have already known this, as it looks like you started to do it, but left the open bracket unclosed.
[:alpha:]是字符类的表达式。要用作正则表达式字符集，它需要额外的括号。您可能已经知道这一点，因为看起来您已经开始这样做了，但未关闭开放的括号。
