POSIX擴展正則表達式是否支持\ d元字符？

Question

我有一個威騰簡單的C程序如下：

#include <stdio.h> 
#include <regex.h> 

int main(int argc, char* argv[]) 
{ 
    regex_t re; 
    char *pattern = "\\d{3}([a-zA-Z]+).(\\d{2}|N/A)\\s\\1"; // use \d, but wouldn't match 
    const char *target = "123Hello N/A Hello"; 

    regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB); 

    int ret = regexec(&re, target, (size_t) 0, NULL, 0); 
    if(ret == REG_NOMATCH) { 
     printf("\n%s\n does not match \n%s\n", target, pattern); 
    } 

    pattern = "[0-9]{3}([a-zA-Z]+).([0-9]{2}|N/A)\\s\\1"; // changes to [0-9], now OK 

    regcomp(&re, pattern, REG_EXTENDED|REG_NOSUB); 

    ret = regexec(&re, target, (size_t) 0, NULL, 0); 
    if(ret == REG_NOMATCH) { 
     printf("\n%s\n does not match \n%s\n", target, pattern); 
    } 

    regfree(&re); 
    return 0; 
} 

我已經閱讀Wikipedia標準的POSIX正則表達式，我還沒有找到該POSIX立場是否suports的\ d元字符的任何證據。

或者我的代碼有一個微妙的錯誤？

Answer 1

據this，POSIX正則表達式不支持\d簡寫（和他們也不支持\w或\s）。