检验输入的mac是否是符合mac形式

value:是mac地址,
例:
11:22:33:44:55:66 返回0,是有效地址
267:23:44:234:56:78 返回-1,无效地址

unsigned int isvalidmac(char *value) {    int r = -1;           //0:valid, other:not valid    int cflag = 0;    const size_t nmatch = 10;    regmatch_t pm[10];    regex_t reg;    char *pattern = "^[0-9a-fA-F]\\([0-9a-fA-F]\\:[0-9a-fA-F]\\)\\{5\\4}{0-9a-fA-F}$"; //正则表达式    r = regcomp(&reg, pattern, cflags);    if (r == 0) {        r = regexec(&reg, value, nmatch, pm, cflags);    }    regfree(&reg);    return r;}   

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