awk - 在awk中用双引号转义分隔符

Question

我正在使用awk来使用“，”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“，”。

例

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

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？

Answer 1

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。

从 GNU awk manual on "Defining fields by content:

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，这对于空白字段无法正常工作，但也可以将其修复:

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