regex - awk 扩展模式匹配（在已匹配字符串的操作中嵌入模式匹配）

Question

我想处理形式的字符串：

PREFIX_TYPE_N,DATA

那么，*awk (gawk, mawk, nawk) 是否支持在已匹配字符串的操作中包含模式匹配？像这样的东西（当然，对我不起作用）：

*awk 'BEGIN { FS="," }
     /PREFIX/ {
                /TYPE_1/  {printf "[TYPE1] [DATA: $2]"}    // <-- included pattern 
                /TYPE_2/  {printf "[TYPE2] [DATA: $2]"}    // <-- another included pattern
                ...                                        // <-- some more included patterns
              }' "filename"

还是我还需要 if/else 或 switch/case？

Answer 1

不完全那样，但非常接近，因为有一个正则表达式匹配运算符 (~)：

BEGIN { FS="," }
/PREFIX/ {
            if ($1 ~ "TYPE_1") {printf "[TYPE1] [DATA: $2]"}    // <-- included pattern 
            if ($1 ~ "TYPE_2") {printf "[TYPE2] [DATA: $2]"}    // <-- another included pattern
            ...                                        // <-- some more included patterns
          }

请注意，因为第一个模式匹配已经进入它的块并且只处理了一行，所以在块中只有 ifs 很好。

如果你真的想要模式的易读性，你可以这样做：

BEGIN { FS="," }
/PREFIX/ { //stuff to do for all prefixes, before specific handling
          data = $2 }
/PREFIX_TYPE_1/ { type = "TYPE_1"; }
/PREFIX_TYPE_2/ { type = "TYPE_2"; }
/PREFIX/ { //stuff to do for all prefixes, after specific handling 
          printf("[%s] [DATA: $2]", type, data)
          }

Answer 2

你可以在 gawk 中这样做：

awk 'BEGIN { FS="," }
     /PREFIX/ {
                if (/TYPE_1/)  {printf "[TYPE1] [DATA: $2]"}    // <-- included pattern 
                if (/TYPE_2/)  {printf "[TYPE2] [DATA: $2]"}    // <-- another included pattern
                ...                                        // <-- some more included patterns
              }' "filename"

这里/TYPE_1/相当于$0 ~ /TYPE_1/. 在文档中查找详细信息（第 6.1.2 部分）。