regex - 如何列出正则表达式字符类的成员，例如 [:punct:]？

Question

例如，我从文档中知道，例如

http://stat.ethz.ch/R-manual/R-devel/library/base/html/regex.html

那

[:punct:]

包括

! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~.

但我想从命令行检查（在我的情况下，是 R，但在 bash 等中可能类似），并列出 [:alpha:] 等。

Answer 1

 grep("[[:punct:]]", unlist(strsplit(rawToChar(as.raw(1:127)), "")), value = TRUE)
 ## [1] "!"  "\"" "#"  "$"  "%"  "&"  "'"  "("  ")"  "*"  "+"  ","  "-"  "."  "/" 
 ## [16] ":"  ";"  "<"  "="  ">"  "?"  "@"  "["  "\\" "]"  "^"  "_"  "`"  "{"  "|" 
 ## [31] "}"  "~" 

gsub("[^[:punct:]]", "", rawToChar(as.raw(1:127)), "")
## [1] "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"

Answer 2

如果您只需要担心 ASCII，那么可能会执行以下操作（使用 bash）：

$ for n in {0..127}; do awk '{ printf("%c", $0); }' <<< $n | grep '[[:punct:]]' | tr '\n' ' '; done
! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~

$ for n in {0..127}; do awk '{ printf("%c", $0); }' <<< $n | grep '[[:alnum:]]' | tr '\n' ' '; done
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