在awk中用双引号转义分隔符 [英] Escaping separator within double quotes, in awk

问题描述

我正在使用awk用，"作为分隔符来解析我的数据，因为输入是一个csv文件.但是，数据中存在用双引号("...")进行转义的，".

I am using awk to parse my data with "," as separator as the input is a csv file. However, there are "," within the data which is escaped by double quotes ("...").

示例

filed1,filed2,field3,"field4,FOO,BAR",field5

我如何忽略双引号中的逗号，"，以便可以使用awk正确解析输出?我知道我们可以在excel中做到这一点，但是我们如何在awk中做到这一点呢?

How can i ignore the comma "," within the the double quote so that I can parse the output correctly using awk? I know we can do this in excel, but how do we do it in awk?

推荐答案

使用 GNU awk 4 很简单:

zsh-4.3.12[t]% awk '{ 
 for (i = 0; ++i <= NF;)
   printf "field %d => %s\n", i, $i
 }' FPAT='([^,]+)|("[^"]+")' infile
field 1 => filed1
field 2 => filed2
field 3 => field3
field 4 => "field4,FOO,BAR"
field 5 => field5

根据OP要求添加一些注释.

Adding some comments as per OP requirement.

来自 GNU关于按内容定义字段:

FPAT的值应为提供常规字符的字符串 表达.此正则表达式描述了每个内容 场地.对于上述CSV数据，每个字段为 不是逗号的任何内容"或双引号，任何内容" 那不是双引号，也不是双引号."如果写成 一个正则表达式常量，我们将有/([^,]+)|("[^"]+")/.将其写为字符串 要求我们转义双引号，从而导致:

The value of FPAT should be a string that provides a regular expression. This regular expression describes the contents of each field. In the case of CSV data as presented above, each field is either "anything that is not a comma," or "a double quote, anything that is not a double quote, and a closing double quote." If written as a regular expression constant, we would have /([^,]+)|("[^"]+")/. Writing this as a string requires us to escape the double quotes, leading to:

FPAT = "([^,]+)|(\"[^\"]+\")"

使用+两次，此操作不适用于空白字段，但也可以修复:

Using + twice, this does not work properly for empty fields, but it can be fixed as well:

按照书面规定，用于FPAT的正则表达式要求每个字段至少包含一个字符.直接修改(将第一个"+"更改为"*")可以使字段为空:

As written, the regexp used for FPAT requires that each field contain at least one character. A straightforward modification (changing the first ‘+’ to ‘*’) allows fields to be empty:

FPAT = "([^,]*)|(\"[^\"]+\")"

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