正则表达式在 CSV 文件中查找未转义的双引号

Question

什么是正则表达式来查找 CSV 文件中由双引号引起的列中包含的 2 个未转义双引号的集合？

不匹配：

"asdf","asdf"
"", "asdf"
"asdf", ""
"adsf", "", "asdf"

匹配：

"asdf""asdf", "asdf"
"asdf", """asdf"""
"asdf", """"

Answer 1

试试这个：

(?m)""(?![ \t]*(,|$))

解释：

(?m)       // enable multi-line matching (^ will act as the start of the line and $ will act as the end of the line (i))
""         // match two successive double quotes
(?!        // start negative look ahead
  [ \t]*   //   zero or more spaces or tabs
  (        //   open group 1
    ,      //     match a comma 
    |      //     OR
    $      //     the end of the line or string
  )        //   close group 1
)          // stop negative look ahead

所以，用简单的英语：“匹配两个连续的双引号，前提是它们前面没有逗号或行尾，中间有可选的空格和制表符”.

(i) 除了是普通的字符串开始和字符串结束元字符。

Answer 2

由于您的问题很复杂，解决方案取决于您使用的引擎。这是因为要解决它，您必须使用向后看和向前看，并且每个引擎都不相同。

我的答案是使用 Ruby 引擎。检查只是一个正则表达式，但我在这里列出了整个代码以便更好地解释它。

请注意，由于 Ruby RegEx 引擎（或我的知识），可选的前瞻/后视是不可能的。所以我需要逗号前后的空格问题。

这是我的代码：

orgTexts = [
    '"asdf","asdf"',
    '"", "asdf"',
    '"asdf", ""',
    '"adsf", "", "asdf"',
    '"asdf""asdf", "asdf"',
    '"asdf", """asdf"""',
    '"asdf", """"'
]

orgTexts.each{|orgText|
    # Preprocessing - Eliminate spaces before and after comma
    # Here is needed if you may have spaces before and after a valid comma
    orgText = orgText.gsub(Regexp.new('\" *, *\"'), '","')

    # Detect valid character (non-quote and valid quote)
    resText = orgText.gsub(Regexp.new('([^\"]|^\"|\"$|(?<=,)\"|\"(?=,)|(?<=\\\\)\")'), '-')
    # resText = orgText.gsub(Regexp.new('([^\"]|(^|(?<=,)|(?<=\\\\))\"|\"($|(?=,)))'), '-')
    # [^\"]       ===> A non qoute
    # |           ===> or
    # ^\"         ===> beginning quot
    # |           ===> or
    # \"$         ===> endding quot
    # |           ===> or
    # (?<=,)\"    ===> quot just after comma
    # \"(?=,)     ===> quot just before comma
    # (?<=\\\\)\" ===> escaped quot

    #  This part is to show the invalid non-escaped quots
    print orgText
    print resText.gsub(Regexp.new('"'), '^')

    # This part is to determine if there is non-escaped quotes
    # Here is the actual matching, use this one if you don't want to know which quote is un-escaped
    isMatch = ((orgText =~ /^([^\"]|^\"|\"$|(?<=,)\"|\"(?=,)|(?<=\\\\)\")*$/) != 0).to_s
    # Basicall, it match it from start to end (^...$) there is only a valid character

    print orgText + ": " + isMatch
    print 
    print ""
    print ""
} 

执行代码时打印：

"asdf","asdf"
-------------
"asdf","asdf": false


"","asdf"
---------
"","asdf": false


"asdf",""
---------
"asdf","": false


"adsf","","asdf"
----------------
"adsf","","asdf": false


"asdf""asdf","asdf"
-----^^------------
"asdf""asdf","asdf": true


"asdf","""asdf"""
--------^^----^^-
"asdf","""asdf""": true


"asdf",""""
--------^^-
"asdf","""": true

我希望我在这里给你一些想法，你可以使用其他引擎和语言。

Answer 3

".*"(\n|(".*",)*)

应该可以，我猜...

Answer 4

对于单行匹配：

^("[^"]*"\s*,\s*)*"[^"]*""[^"]*"

或多行：

(^|\r\n)("[^\r\n"]*"\s*,\s*)*"[^\r\n"]*""[^\r\n"]*"

编辑/注意：根据所使用的正则表达式引擎，您可以使用lookbehinds 和其他东西来使正则表达式更精简。但这应该适用于大多数正则表达式引擎。

Answer 5

试试这个正则表达式：

"(?:[^",\\]*|\\.)*(?:""(?:[^",\\]*|\\.)*)+"

这将匹配带有至少一对非转义双引号的任何带引号的字符串。